install_package "yaml-0.1.6" "http://pyyaml.org/download/libyaml/yaml-0.1.6.tar.gz#7da6971b4bd08a986dd2a61353bc422362bd0edcc67d7ebaac68c95f74182749" --if needs_yaml
install_git "ruby-1.9.3-dev" "https://github.com/ruby/ruby.git" "ruby_1_9_3" autoconf standard