title: Why do I get a bcrypt-ruby gem install error?
body: <p>Getting an error when trying to install the gem devise, the installation is stopping on
  the gem bcrypt-ruby: </p>
  
  <pre><code>$ gem install bcrypt-ruby
  Error installing bcrypt-ruby:
  ERROR: Failed to build gem native extension.
  </code></pre>
  
  <p>I'm running OSX 10.6.7 with Ruby under RVM.
  I reinstalled the lastest version of xcode &amp; reinstalled Ruby 64bit, Rails and all the gems. </p>