title: `gem install therubyracer` fails on Mac OS X Lion
body: <p>I would appreciate some help in getting <code>gem install therubyracer</code> to work. Here is the error:</p>
  
  <pre><code>$ gem install therubyracer
  Building native extensions.  This could take a while...
  ERROR:  Error installing therubyracer:
      ERROR: Failed to build gem native extension.
  
          /Users/david/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
  checking for main() in -lobjc... yes
  *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of
  necessary libraries and/or headers.  Check the mkmf.log file for more
  details.  You may need configuration options.
  
  Provided configuration options:
      --with-opt-dir
      --with-opt-include
      --without-opt-include=${opt-dir}/include
      --with-opt-lib
      --without-opt-lib=${opt-dir}/lib
      --with-make-prog
      --without-make-prog
      --srcdir=.
      --curdir
      --ruby=/Users/david/.rvm/rubies/ruby-1.9.3-p194/bin/ruby
      --with-objclib
      --without-objclib
  extconf.rb:15:in `&lt;main&gt;': undefined method `include_path' for Libv8:Module (NoMethodError)
  </code></pre>
  
  <p>Here are some notable steps that I ran before the error. They worked fine:</p>
  
  <pre><code>$ gem install libv8
  $ brew install v8
  </code></pre>
  
  <p>My environment is:</p>
  
  <ul>
  <li>Mac OS X Lion 10.7.4</li>
  <li>ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-darwin11.4.0] (via rvm)</li>
  <li>V8 version 3.9.24 (via homebrew)</li>
  </ul>