title: Install Rails Failed on OSX 10.8.4
body: <p>I always failed to install rails on my new Air with OSX 10.8.4, even I succeed installed ruby2, Command Line Tool of XCode, it still prompts some error when I try to install rails.</p>
  
  <p>I found lots solutions from the Internet, but they all don't work on my issue, I'm completely confused, doesn't any can help me? I'll really appreciate!!!</p>
  
  <hr>
  
  <pre><code>    localhost:myapp zerocool$ ruby -v
  ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.3.0]
  localhost:myapp zerocool$ sudo gem install rails
  Password:
  Building native extensions.  This could take a while...
  ERROR:  Error installing rails:
      ERROR: Failed to build gem native extension.
  
      /Users/zerocool/.rvm/rubies/ruby-2.0.0-p247/bin/ruby extconf.rb
  *** 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
      --without-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/zerocool/.rvm/rubies/ruby-2.0.0-p247/bin/ruby
      --with-atomic_reference-dir
      --without-atomic_reference-dir
      --with-atomic_reference-include
      --without-atomic_reference-include=${atomic_reference-dir}/include
      --with-atomic_reference-lib
      --without-atomic_reference-lib=${atomic_reference-dir}/
  /Users/zerocool/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/mkmf.rb:434:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
  You have to install development tools first.
      from /Users/zerocool/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/mkmf.rb:519:in `try_link0'
      from /Users/zerocool/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/mkmf.rb:817:in `try_run'
      from extconf.rb:24:in `&lt;main&gt;'
  
  
  Gem files will remain installed in /Users/zerocool/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/gems/2.0.0/gems/atomic-1.1.12 for inspection.
  Results logged to /Users/zerocool/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/gems/2.0.0/gems/atomic-1.1.12/ext/gem_make.out
  </code></pre>