How do I install the libv8 ruby gem on a fresh Mountain Lion install?

Question

I've been racking my head on this one. I've followed suggestions in several related posts but to no avail.

I am starting from a fresh install of Mountain Lion, installed the Command Line Tools, and have Ruby 1.8.7 successfully installed based on a few other posts I've found for installing gcc-4.2 via Homebrew and adding a symlink to /usr/bin/gcc-4.2.

Now, however, I'm unable to successfully install libv8. The error below is as far as I've gotten off of the existing suggestions.

Any additional input?

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /Users/Eric/.rbenv/versions/1.8.7-p352/bin/ruby extconf.rb 
creating Makefile
Unable to find a compiler officially supported by v8.
It is recommended to use GCC v4.4 or higher
Traceback (most recent call last):
  File "build/gyp/gyp", line 18, in <module>
    sys.exit(gyp.main(sys.argv[1:]))
  File "build/gyp/pylib/gyp/__init__.py", line 480, in main
    generator.GenerateOutput(flat_list, targets, data, params)
  File "build/gyp/pylib/gyp/generator/make.py", line 2085, in GenerateOutput
    part_of_all=qualified_target in needed_targets)
  File "build/gyp/pylib/gyp/generator/make.py", line 756, in Write
    self.xcode_settings, self.Absolutify, self.Pchify))
  File "build/gyp/pylib/gyp/generator/make.py", line 1132, in WriteSources
    cflags = self.xcode_settings.GetCflags(configname)
  File "build/gyp/pylib/gyp/xcode_emulation.py", line 258, in GetCflags
    sdk_root = self._SdkPath()
  File "build/gyp/pylib/gyp/xcode_emulation.py", line 247, in _SdkPath
    return os.path.join(self._GetSdkBaseDir(), '%s.sdk' % sdk_root)
  File "build/gyp/pylib/gyp/xcode_emulation.py", line 233, in _GetSdkBaseDir
    raise Exception('Error %d running xcode-select' % job.returncode)
Exception: Error 2 running xcode-select
make: *** [out/Makefile.x64] Error 1
Using compiler: g++
GYP_GENERATORS=make \
    build/gyp/gyp --generator-output="out" build/all.gyp \
                  -Ibuild/standalone.gypi --depth=. \
                  -Dv8_target_arch=x64 \
                  -S.x64 -Dhost_arch=x64
xcode-select: Error: No Xcode is selected. Use xcode-select -switch <path-to-xcode>, or see the xcode-select manpage (man xcode-select) for further information.



Gem files will remain installed in /Users/Eric/Development/par8o/vendor/bundle/ruby/1.8/gems/libv8-3.11.8.3 for inspection.
Results logged to /Users/Eric/Development/par8o/vendor/bundle/ruby/1.8/gems/libv8-3.11.8.3/ext/libv8/gem_make.out
An error occured while installing libv8 (3.11.8.3), and Bundler cannot continue.
Make sure that `gem install libv8 -v '3.11.8.3'` succeeds before bundling.

Answer 1

The deal is with ruby 1.8.7. Probably you need this gem to run therubyracer. And to make this work you need install therubyracer gem as follows:

RUBYOPT=-rrubygems gem install therubyracer

This will install both therubyracer and libv8 gems.

source: http://coderwall.com/p/y1djxq