title: RubyInstaller - ERROR: Failed to build gem native extension
body: <p>I installed <strong>RailsInstaller</strong> and added <code>DevKit</code> and <code>DevKit/mingw</code> to <code>PATH</code><br>
  When I execute <code>bundle install</code> I got:</p>
  
  <pre><code>ERROR: Failed to build gem native extension.
  
  "C:/Program Files (x86)/RailsInstaller/Ruby1.9.3/bin/ruby.exe" extconf.rb
  C:/Program Files (x86)/RailsInstaller/Ruby1.9.3/bin/ruby.exe: invalid switch in RUBYOPT: -F (RuntimeError)
  </code></pre>
  
  <p><code>OS : Windows 8 x64, Administrator Account</code></p>