Appcompat v7 isn't pulled into project

Question

I inherited a project which uses appcompat-v7:20.0.0
I'm not able to build the project, because it seems that gradle doesn't include the appcompat library while synching/building.

My dependencies in the build.gradle:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:20.0.0'
    compile 'com.nineoldandroids:library:2.4.0'
    compile 'com.google.android.gms:play-services:+'
}

Also no play services are pulled into the project, but nine old androids is(I tried including different libraries, it seemed that everything from jcenter is downloaded) As you can see in the following screenshot:

The gradle plugin is 1.0.0 and there are no problems during synching.
Are there any known solutions to such type of problem?

EDIT 1:
Android Support Repository
Android Support Library
Google Play Services
Are all installed. However it also works for newly created projects.

EDIT 2:

The ./gradlew build output:

Caused by: org.gradle.internal.UncheckedException: com.android.ide.common.internal.LoggedErrorException: Failed to run command:
/Users/stephan/Library/Android/sdk/build-tools/20.0.0/aapt package -f --no-crunch -I /Users/stephan/Library/Android/sdk/platforms/android-21/android.jar -M /Users/project-path/build/intermediates/manifests/full/flavor/beta/AndroidManifest.xml -S /Users/project-path/build/intermediates/res/flavor/beta -A /Users/project-path/build/intermediates/assets/flavor/beta -m -J /Users/project-path/build/generated/source/r/flavor/beta -F /Users/project-path/build/intermediates/res/resources-flavor-beta.ap_ --debug-mode --custom-package de.my.project -0 apk --output-text-symbols /Users/project-path/build/intermediates/symbols/flavor/beta
Error Code:
1
Output:
/Users/project-path/build/intermediates/res/flavor/beta/values/values.xml:2127: error: Error retrieving parent for item: No resource found that matches the given name 'Widget.AppCompat.Light.Base.Spinner'.
/Users/project-path/build/intermediates/res/flavor/beta/values-v16/values.xml:89: error: Error retrieving parent for item: No resource found that matches the given name 'Widget.AppCompat.Light.Base.Spinner'.

I also checked Widget.AppCompat.Light.Base.Spinner is part of the values.xml in appcompat-v7 20.0.0
Here are the sdk versions:

compileSdkVersion "Google Inc.:Google APIs:21"
buildToolsVersion "20.0.0"

defaultConfig {
    minSdkVersion 10
    targetSdkVersion 17
}

EDIT 3:

Project root build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.0.0'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

App build.gradle

apply plugin: 'com.android.application'

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])

    compile 'com.android.support:appcompat-v7:20.0.0'
    compile 'com.nineoldandroids:library:2.4.0'
    compile 'com.google.android.gms:play-services:+'

}

android {
    compileSdkVersion "Google Inc.:Google APIs:21"
    buildToolsVersion "20.0.0"

    defaultConfig {
        minSdkVersion 10
        targetSdkVersion 17
    }

    packagingOptions {
        exclude 'META-INF/LICENSE.txt'
    }

    signingConfigs {
        conf1 {
            storeFile file("path")
            storePassword ""
            keyAlias ""
            keyPassword ""
        }

        debug {
            storeFile file("path")
            storePassword ""
            keyAlias ""
            keyPassword ""
        }
    }

    buildTypes {
        debug {
            zipAlignEnabled true
            minifyEnabled false
            proguardFile getDefaultProguardFile('proguard-android.txt')
            proguardFile 'proguard-project.txt'
            signingConfig signingConfigs.debug
        }

        release {
            zipAlignEnabled true
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt')
            proguardFiles 'proguard-rules.pro'
        }

        beta {
            initWith debug
            signingConfig signingConfigs.debug
        }
    }

    productFlavors {
        flavor1 {
            applicationId "de.package"
            versionCode 1
            versionName "1.0"
            signingConfig signingConfigs.conf1
        }
    }


    lintOptions {
        checkReleaseBuilds false
        abortOnError false
    }
}

Answer 1

I read the documentation for the Android appcompat library and it says that this library depends of v4 support library so you need include this in your project this is the link :https://developer.android.com/tools/support-library/features.html

You only need to change the dependencies in the build.gradle file and add the following line
compile 'com.android.support:support-v4:22.2.1' You can change the version(22.2.1) and put the version 20.0.0 if you want