How do I print a list of "Build Settings" in Xcode project?

Question

UPDATE: This list is getting a little out dated (it was generated with Xcode 4.1). You should run the command suggested by dunedin15.

dunedin15's answer can give inaccurate results for some edge-cases, such as when debugging build settings of a static lib for an Archive build, see Slipp D. Thompson's answer for a more robust output.

Original Answer

Variable                                  Example
PATH                                      "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
LANG                                      en_US.US-ASCII
IPHONEOS_DEPLOYMENT_TARGET                4.1
ACTION                                    build
AD_HOC_CODE_SIGNING_ALLOWED               NO
ALTERNATE_GROUP                           staff
ALTERNATE_MODE                            u+w,go-w,a+rX
ALTERNATE_OWNER                           username
ALWAYS_SEARCH_USER_PATHS                  YES
APPLE_INTERNAL_DEVELOPER_DIR              /AppleInternal/Developer
APPLE_INTERNAL_DIR                        /AppleInternal
APPLE_INTERNAL_DOCUMENTATION_DIR          /AppleInternal/Documentation
APPLE_INTERNAL_LIBRARY_DIR                /AppleInternal/Library
APPLE_INTERNAL_TOOLS                      /AppleInternal/Developer/Tools
APPLY_RULES_IN_COPY_FILES                 NO
ARCHS                                     "armv6 armv7"
ARCHS_STANDARD_32_64_BIT                  "armv6 armv7"
ARCHS_STANDARD_32_BIT                     "armv6 armv7"
ARCHS_UNIVERSAL_IPHONE_OS                 armv7
AVAILABLE_PLATFORMS                       "iphonesimulator macosx iphoneos"
BUILD_COMPONENTS                          "headers build"
BUILD_DIR                                 "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath"
BUILD_ROOT                                "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath"
BUILD_STYLE                    
BUILD_VARIANTS                             normal
BUILT_PRODUCTS_DIR                         "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos"
CACHE_ROOT                                 /var/folders/2x/rvb2r9s16mq6r318zxvn0lk80000gn/C/com.apple.Xcode.501
CCHROOT                                    /var/folders/2x/rvb2r9s16mq6r318zxvn0lk80000gn/C/com.apple.Xcode.501
CHMOD                                      /bin/chmod
CHOWN                                      /usr/sbin/chown
CLASS_FILE_DIR                             "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/JavaClasses"
CLEAN_PRECOMPS                             YES
CLONE_HEADERS                              NO
CODESIGNING_FOLDER_PATH                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation/Applications/project.app"
CODE_SIGNING_ALLOWED                       YES
CODE_SIGNING_REQUIRED                      YES
CODE_SIGN_CONTEXT_CLASS                    XCiPhoneOSCodeSignContext
CODE_SIGN_IDENTITY                         "iPhone Distribution"
COMBINE_HIDPI_IMAGES                       NO
COMPOSITE_SDK_DIRS                         /var/folders/2x/rvb2r9s16mq6r318zxvn0lk80000gn/C/com.apple.Xcode.501/CompositeSDKs
COMPRESS_PNG_FILES                         YES
CONFIGURATION                              Distribution
CONFIGURATION_BUILD_DIR                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos"
CONFIGURATION_TEMP_DIR                     "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos"
CONTENTS_FOLDER_PATH                       project.app/Contents
COPYING_PRESERVES_HFS_DATA                 NO
COPY_PHASE_STRIP                           YES
COPY_RESOURCES_FROM_STATIC_FRAMEWORKS      YES
CP                                         /bin/cp
CURRENT_ARCH                               armv7
CURRENT_VARIANT                            normal
DEAD_CODE_STRIPPING                        YES
DEBUGGING_SYMBOLS                          YES
DEBUG_INFORMATION_FORMAT                   dwarf-with-dsym
DEPLOYMENT_LOCATION                        YES
DEPLOYMENT_POSTPROCESSING                  YES
DERIVED_FILES_DIR                          "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources"
DERIVED_FILE_DIR                           "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources"
DERIVED_SOURCES_DIR                        "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources"
DEVELOPER_APPLICATIONS_DIR                 /Developer/Applications
DEVELOPER_BIN_DIR                          /Developer/usr/bin
DEVELOPER_DIR                              /Developer
DEVELOPER_FRAMEWORKS_DIR                   /Developer/Library/Frameworks
DEVELOPER_FRAMEWORKS_DIR_QUOTED            "\"/Developer/Library/Frameworks\""
DEVELOPER_LIBRARY_DIR                      /Developer/Library
DEVELOPER_SDK_DIR                          /Developer/SDKs
DEVELOPER_TOOLS_DIR                        /Developer/Tools
DEVELOPER_USR_DIR                          /Developer/usr
DEVELOPMENT_LANGUAGE                       English
DOCUMENTATION_FOLDER_PATH                  project.app/English.lproj/Documentation
DO_HEADER_SCANNING_IN_JAM                  NO
DSTROOT                                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation"
DWARF_DSYM_FILE_NAME                       project.app.dSYM
DWARF_DSYM_FILE_SHOULD_ACCOMPANY_PRODUCT   NO
DWARF_DSYM_FOLDER_PATH                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos"
EFFECTIVE_PLATFORM_NAME                    -iphoneos
EMBEDDED_PROFILE_NAME                      embedded.mobileprovision
ENABLE_HEADER_DEPENDENCIES                 YES
ENABLE_OPENMP_SUPPORT                      NO
ENTITLEMENTS_ALLOWED                       YES
ENTITLEMENTS_REQUIRED                      YES
EXCLUDED_INSTALLSRC_SUBDIRECTORY_PATTERNS  ".svn CVS"
EXECUTABLES_FOLDER_PATH                    project.app/Executables
EXECUTABLE_FOLDER_PATH                     project.app
EXECUTABLE_NAME                            project
EXECUTABLE_PATH                            project.app/project
FILE_LIST                                  "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/Objects/LinkFileList"
FIXED_FILES_DIR                            "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/FixedFiles"
FRAMEWORKS_FOLDER_PATH                     project.app/Frameworks
FRAMEWORK_FLAG_PREFIX                      -framework
FRAMEWORK_SEARCH_PATHS                     "\"/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos\" "
FRAMEWORK_VERSION                          A
FULL_PRODUCT_NAME                          project.app
GCC3_VERSION                               3.3
GCC_C_LANGUAGE_STANDARD                    gnu99
GCC_INLINES_ARE_PRIVATE_EXTERN             YES
GCC_PFE_FILE_C_DIALECTS                    "c objective-c c++ objective-c++"
GCC_PRECOMPILE_PREFIX_HEADER               YES
GCC_PREFIX_HEADER                          project/Prefix.pch
GCC_PREPROCESSOR_DEFINITIONS               "NDEBUG DISTRIBUTION_BUILD=1 KK_TARGET=0x000F0"
GCC_SYMBOLS_PRIVATE_EXTERN                 YES
GCC_THUMB_SUPPORT                          YES
GCC_TREAT_WARNINGS_AS_ERRORS               NO
GCC_VERSION                                com.apple.compilers.llvm.clang.1_0
GCC_VERSION_IDENTIFIER                     com_apple_compilers_llvm_clang_1_0
GCC_WARN_ABOUT_RETURN_TYPE                 YES
GCC_WARN_UNUSED_FUNCTION                   YES
GCC_WARN_UNUSED_VARIABLE                   YES
GENERATE_MASTER_OBJECT_FILE                NO
GENERATE_PKGINFO_FILE                      YES
GENERATE_PROFILING_CODE                    NO
GID                                        20
GROUP                                      staff
INPUT_FILE_BASE             Default
INPUT_FILE_DIR              "/Volumes/Development/Project Game/Project-v1/images"
INPUT_FILE_NAME             Default.png
INPUT_FILE_PATH             "/Volumes/Development/Project Game/Project-v1/images/Default.png"
SCRIPT_INPUT_FILE           "/Volumes/Development/Project Game/Project-v1/images/Default.png"
SCRIPT_OUTPUT_FILE_0        "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources/Default.png"

EXCLUDED_RECURSIVE_SEARCH_PATH_SUBDIRECTORIES              "*.nib *.lproj *.framework *.gch (*) CVS .svn .git *.xcodeproj *.xcode *.pbproj *.pbxproj"
HEADERMAP_INCLUDES_FLAT_ENTRIES_FOR_TARGET_BEING_BUILT     YES
HEADERMAP_INCLUDES_FRAMEWORK_ENTRIES_FOR_ALL_PRODUCT_TYPES YES
HEADERMAP_INCLUDES_NONPUBLIC_NONPRIVATE_HEADERS            YES
HEADERMAP_INCLUDES_PROJECT_HEADERS                         YES
HEADER_SEARCH_PATHS                  "\"/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos/include\" "
ICONV                                /usr/bin/iconv
INFOPLIST_EXPAND_BUILD_SETTINGS      YES
INFOPLIST_FILE                       project/Resources/Info.plist
INFOPLIST_OUTPUT_FORMAT              binary
INFOPLIST_PATH                       project.app/Info.plist
INFOPLIST_PREPROCESS                 NO
INFOSTRINGS_PATH                     project.app/English.lproj/InfoPlist.strings
INPUT_FILE_REGION_PATH_COMPONENT                    
INPUT_FILE_SUFFIX                    .png
INSTALL_DIR                          "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation/Applications"
INSTALL_GROUP                        staff
INSTALL_MODE_FLAG                    u+w,go-w,a+rX
INSTALL_OWNER                        username
INSTALL_PATH                         /Applications
INSTALL_ROOT                         "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation"
JAVAC_DEFAULT_FLAGS                  "-J-Xms64m -J-XX:NewSize=4M -J-Dfile.encoding=UTF8"
JAVA_APP_STUB                        /System/Library/Frameworks/JavaVM.framework/Resources/MacOS/JavaApplicationStub
JAVA_ARCHIVE_CLASSES                 YES
JAVA_ARCHIVE_TYPE                    JAR
JAVA_COMPILER                        /usr/bin/javac
JAVA_FOLDER_PATH                     project.app/Java
JAVA_FRAMEWORK_RESOURCES_DIRS        Resources
JAVA_JAR_FLAGS                       cv
JAVA_SOURCE_SUBDIR                   .
JAVA_USE_DEPENDENCIES                YES
JAVA_ZIP_FLAGS                       -urg
JIKES_DEFAULT_FLAGS                  "+E +OLDCSO"
KEEP_PRIVATE_EXTERNS                 NO
LD_GENERATE_MAP_FILE                 NO
LD_MAP_FILE_PATH                     "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/project-LinkMap-normal-armv7.txt"
LD_NO_PIE                            NO
LD_OPENMP_FLAGS                      -fopenmp
LEGACY_DEVELOPER_DIR                 /Developer/Library/Xcode/PrivatePlugIns/Xcode3Core.ideplugin/Contents/SharedSupport/Developer
LEX                                  /Developer/usr/bin/lex
LIBRARY_FLAG_NOSPACE                 YES
LIBRARY_FLAG_PREFIX                  -l
LIBRARY_SEARCH_PATHS                 "\"/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos\"  \"/Volumes/Development/Project Game/Project-v1/FlurryLib\""
LINKER_DISPLAYS_MANGLED_NAMES        NO
LINK_FILE_LIST_normal_armv6          "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/Objects-normal/armv6/project.LinkFileList"
LINK_FILE_LIST_normal_armv7          "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/Objects-normal/armv7/project.LinkFileList"
LINK_WITH_STANDARD_LIBRARIES         YES
LOCALIZED_RESOURCES_FOLDER_PATH      project.app/English.lproj
LOCAL_ADMIN_APPS_DIR                 /Applications/Utilities
LOCAL_APPS_DIR                       /Applications
LOCAL_DEVELOPER_DIR                  /Library/Developer
LOCAL_LIBRARY_DIR                    /Library
MACH_O_TYPE                          mh_execute
MAC_OS_X_PRODUCT_BUILD_VERSION       11A511
MAC_OS_X_VERSION_ACTUAL              1070
MAC_OS_X_VERSION_MAJOR               1070
MAC_OS_X_VERSION_MINOR               0700
NATIVE_ARCH                          armv6
NATIVE_ARCH_32_BIT                   i386
NATIVE_ARCH_64_BIT                   x86_64
NATIVE_ARCH_ACTUAL                   x86_64
NO_COMMON                            YES
OBJECT_FILE_DIR                      "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/Objects"
OBJECT_FILE_DIR_normal               "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/Objects-normal"
OBJROOT                              "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath"
ONLY_ACTIVE_ARCH                     NO
OPTIMIZATION_LEVEL                   0
OS                                   MACOS
OSAC                                 /usr/bin/osacompile
OTHER_CFLAGS                         -DNS_BLOCK_ASSERTIONS=1
OTHER_CPLUSPLUSFLAGS                 -DNS_BLOCK_ASSERTIONS=1
OTHER_INPUT_FILE_FLAGS                    
OTHER_LDFLAGS                        -lz
PACKAGE_TYPE                         com.apple.package-type.wrapper.application
PASCAL_STRINGS                       YES
PATH_PREFIXES_EXCLUDED_FROM_HEADER_DEPENDENCIES  "/usr/include /usr/local/include /System/Library/Frameworks /System/Library/PrivateFrameworks /Developer/Headers /Developer/SDKs /Developer/Platforms"
PBDEVELOPMENTPLIST_PATH              project.app/pbdevelopment.plist
PFE_FILE_C_DIALECTS                  "c objective-c c++ objective-c++"
PKGINFO_FILE_PATH                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/PkgInfo"
PKGINFO_PATH                         project.app/PkgInfo
PLATFORM_DEVELOPER_APPLICATIONS_DIR  /Developer/Platforms/iPhoneOS.platform/Developer/Applications
PLATFORM_DEVELOPER_BIN_DIR           /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin
PLATFORM_DEVELOPER_LIBRARY_DIR       /Developer/Library/Xcode/PrivatePlugIns/Xcode3Core.ideplugin/Contents/SharedSupport/Developer/Library
PLATFORM_DEVELOPER_SDK_DIR           /Developer/Platforms/iPhoneOS.platform/Developer/SDKs
PLATFORM_DEVELOPER_TOOLS_DIR         /Developer/Platforms/iPhoneOS.platform/Developer/Tools
PLATFORM_DEVELOPER_USR_DIR           /Developer/Platforms/iPhoneOS.platform/Developer/usr
PLATFORM_DIR                         /Developer/Platforms/iPhoneOS.platform
PLATFORM_NAME                        iphoneos
PLATFORM_PREFERRED_ARCH              i386
PLATFORM_PRODUCT_BUILD_VERSION       8H7
PLIST_FILE_OUTPUT_FORMAT             binary
PLUGINS_FOLDER_PATH                  project.app/PlugIns
PRECOMPS_INCLUDE_HEADERS_FROM_BUILT_PRODUCTS_DIR                    YES
PRECOMP_DESTINATION_DIR              "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/PrefixHeaders"
PRESERVE_DEAD_CODE_INITS_AND_TERMS   NO
PRIVATE_HEADERS_FOLDER_PATH          project.app/PrivateHeaders
PRODUCT_NAME                         project
PRODUCT_SETTINGS_PATH                "/Volumes/Development/Project Game/Project-v1/project/Resources/Info.plist"
PRODUCT_TYPE                         com.apple.product-type.application
PROFILING_CODE                       NO
PROJECT                              project
PROJECT_DERIVED_FILE_DIR             "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/DerivedSources"
PROJECT_DIR                          "/Volumes/Development/Project Game/Project-v1"
PROJECT_FILE_PATH                    "/Volumes/Development/Project Game/Project-v1/project.xcodeproj"
PROJECT_NAME                         project
PROJECT_TEMP_DIR                     "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build"
PROVISIONING_PROFILE_REQUIRED        YES
PUBLIC_HEADERS_FOLDER_PATH           project.app/Headers
RECURSIVE_SEARCH_PATHS_FOLLOW_SYMLINKS   YES
REMOVE_CVS_FROM_RESOURCES            YES
REMOVE_GIT_FROM_RESOURCES            YES
REMOVE_SVN_FROM_RESOURCES            YES
RESOURCE_RULES_REQUIRED              YES
REZ_COLLECTOR_DIR                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/ResourceManagerResources"
REZ_OBJECTS_DIR                      "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/ResourceManagerResources/Objects"
REZ_SEARCH_PATHS                     "\"/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos\" "
RUN_CLANG_STATIC_ANALYZER            NO
SCAN_ALL_SOURCE_FILES_FOR_INCLUDES   NO
SCRIPTS_FOLDER_PATH                  project.app/Scripts
SCRIPT_INPUT_FILE                    "/Volumes/Development/Project Game/Project-v1/fonts/helvetica-black-hd.png"
SCRIPT_OUTPUT_FILE_0                 "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build/DerivedSources/helvetica-black-hd.png"
SCRIPT_OUTPUT_FILE_COUNT             1
SDKROOT                              /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk
SDK_DIR                              /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.3.sdk
SDK_NAME                             iphoneos4.3
SDK_PRODUCT_BUILD_VERSION            8H7
SED                                  /usr/bin/sed
SEPARATE_STRIP                       NO
SEPARATE_SYMBOL_EDIT                 NO
SET_DIR_MODE_OWNER_GROUP            YES
SET_FILE_MODE_OWNER_GROUP           NO
SHALLOW_BUNDLE                      YES
SHARED_DERIVED_FILE_DIR             "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath/Distribution-iphoneos/DerivedSources"
SHARED_FRAMEWORKS_FOLDER_PATH       project.app/SharedFrameworks
SHARED_PRECOMPS_DIR                 /Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/Build/PrecompiledHeaders
SHARED_SUPPORT_FOLDER_PATH          project.app/SharedSupport
SKIP_INSTALL                        NO
SOURCE_ROOT                         "/Volumes/Development/Project Game/Project-v1"
SRCROOT                             "/Volumes/Development/Project Game/Project-v1"
STRINGS_FILE_OUTPUT_ENCODING        binary
STRIP_INSTALLED_PRODUCT             YES
STRIP_STYLE                         all
SUPPORTED_DEVICE_FAMILIES           1,2
SUPPORTED_PLATFORMS                 "iphonesimulator iphoneos"
SYMROOT                             "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/BuildProductsPath"
SYSTEM_ADMIN_APPS_DIR               /Applications/Utilities
SYSTEM_APPS_DIR                     /Applications
SYSTEM_CORE_SERVICES_DIR            /System/Library/CoreServices
SYSTEM_DEMOS_DIR                    /Applications/Extras
SYSTEM_DEVELOPER_APPS_DIR           /Developer/Applications
SYSTEM_DEVELOPER_BIN_DIR            /Developer/usr/bin
SYSTEM_DEVELOPER_DEMOS_DIR          "/Developer/Applications/Utilities/Built Examples"
SYSTEM_DEVELOPER_DIR                /Developer
SYSTEM_DEVELOPER_DOC_DIR            "/Developer/ADC Reference Library"
SYSTEM_DEVELOPER_GRAPHICS_TOOLS_DIR "/Developer/Applications/Graphics Tools"
SYSTEM_DEVELOPER_JAVA_TOOLS_DIR     "/Developer/Applications/Java Tools"
SYSTEM_DEVELOPER_PERFORMANCE_TOOLS_DIR   "/Developer/Applications/Performance Tools"
SYSTEM_DEVELOPER_RELEASENOTES_DIR   "/Developer/ADC Reference Library/releasenotes"
SYSTEM_DEVELOPER_TOOLS              /Developer/Tools
SYSTEM_DEVELOPER_TOOLS_DOC_DIR      "/Developer/ADC Reference Library/documentation/DeveloperTools"
SYSTEM_DEVELOPER_TOOLS_RELEASENOTES_DIR   "/Developer/ADC Reference Library/releasenotes/DeveloperTools"
SYSTEM_DEVELOPER_USR_DIR            /Developer/usr
SYSTEM_DEVELOPER_UTILITIES_DIR      /Developer/Applications/Utilities
SYSTEM_DOCUMENTATION_DIR            /Library/Documentation
SYSTEM_LIBRARY_DIR                  /System/Library
TARGETED_DEVICE_FAMILY              1
TARGETNAME                          Project
TARGET_BUILD_DIR                    "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/InstallationBuildProductsLocation/Applications"
TARGET_NAME                         Project
TARGET_TEMP_DIR                     "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build"
TEMP_DIR                            "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build"
TEMP_FILES_DIR                      "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build"
TEMP_FILE_DIR                       "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath/project.build/Distribution-iphoneos/Project.build"
TEMP_ROOT                           "/Users/username/Library/Developer/Xcode/DerivedData/project-dxdgjvgsvvbhowgjqouevhmvgxgf/ArchiveIntermediates/Project Distribution/IntermediateBuildFilesPath"
TEST_AFTER_BUILD                    NO
UID                                 501
UNLOCALIZED_RESOURCES_FOLDER_PATH   project.app    UNSTRIPPED_PRODUCT           NO
USER                         username
USER_APPS_DIR                /Users/username/Applications
USER_HEADER_SEARCH_PATHS     project/libs
USER_LIBRARY_DIR             /Users/username/Library
USE_DYNAMIC_NO_PIC           YES
USE_HEADERMAP                YES
USE_HEADER_SYMLINKS          NO
VALIDATE_PRODUCT             YES
VALID_ARCHS                  "armv6 armv7"
VERBOSE_PBXCP                NO
VERSIONPLIST_PATH            project.app/version.plist
VERSION_INFO_BUILDER         username
VERSION_INFO_FILE            project_vers.c
VERSION_INFO_STRING          "\"@(#)PROGRAM:project  PROJECT:project-\""
WRAPPER_EXTENSION            app
WRAPPER_NAME                 project.app
WRAPPER_SUFFIX               .app
XCODE_APP_SUPPORT_DIR        /Developer/Library/Xcode
XCODE_PRODUCT_BUILD_VERSION  4B110
XCODE_VERSION_ACTUAL         0410
XCODE_VERSION_MAJOR          0400
XCODE_VERSION_MINOR          0410
YACC                        /Developer/usr/bin/yacc

You can also get this information from the command line using the xcodebuild command with the -showBuildSettings switch:

$ xcodebuild -project myProj.xcodeproj -target "myTarg" -showBuildSettings

This will dump a list like the one shown above to the standard output.

Although @dunedin15's fantastic answer has served me well on a number of occasions, it can give inaccurate results for some edge-cases, such as when debugging build settings of a static lib for an Archive build.

As an alternative, a Run Script Build Phase can be easily added to any target to “Log Build Settings” when it's built:

To add, (with the target in question selected) under the Build Phases tab-section click the little ➕ button a dozen-or-so pixels up-left-ward from the Target Dependencies section, and set the shell to /bin/bash and the command to export.  You'll also probably want to drag the phase upwards so that it happens just after Target Dependencies and before Copy Headers or Compile Sources.  Renaming the phase from “Run Script” to “Log Build Settings” isn't a bad idea.

The result is this incredibly helpful listing of current environment variables used for building:

Apple's "Build Setting Reference" documentation for what's officially documented (or as rjstelling's answer shows, use env in a build script to see what Xcode actually passes you.

In case the above link changes, Google search for: "build setting reference" site:developer.apple.com

This has been answered above, but I wanted to suggest an alternative.

When in the Build Settings for you project or target, you can go to the Editor menu and select Show Setting Names from the menu. This will change all of the options in the Build Settings pane to the build variable names. The option in the menu changes to Show Setting Titles, select this to change back to the original view.

This can be handy when you know what build setting you want to use in a script, toggle the setting names in the menu and you can see the variable name.