Installing ffi (0.5.4) from rubygems repository at http://gemcutter.org with native extensions /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/ site_ruby/1.9.1/rubygems/installer.rb:504:in `rescue in block in build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)
rake RUBYARCHDIR=/Users/kristianconsult/my_rails/rails3_apps/demo_app/ vendor/gems/ffi-0.5.4/lib RUBYLIBDIR=/Users/kristianconsult/my_rails/ rails3_apps/demo_app/vendor/gems/ffi-0.5.4/lib /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/rubygems.rb: 827:in `report_activate_error': Could not find RubyGem rake (>= 0) (Gem::LoadError) from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/ rubygems.rb:261:in `activate' from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/ rubygems.rb:68:in `gem' from <internal:gem_prelude>:273:in `push_gem_version_on_load_path' from <internal:gem_prelude>:14:in `gem' from /usr/local/bin/rake:18:in `<main>'
How can I resolve this?
Gemfile