title: How do I install the libv8 ruby gem on a fresh Mountain Lion install?
body: <p>I've been racking my head on this one.  I've followed suggestions in several related posts but to no avail.</p>
  
  <p>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.</p>
  
  <p>Now, however, I'm unable to successfully install libv8.  The error below is as far as I've gotten off of the existing suggestions.  </p>
  
  <p>Any additional input?</p>
  
  <pre><code>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 &lt;module&gt;
      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 &lt;path-to-xcode&gt;, 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.
  </code></pre>