install_package "yaml-0.1.6" "http://pyyaml.org/download/libyaml/yaml-0.1.6.tar.gz#5fe00cda18ca5daeb43762b80c38e06e" --if needs_yaml
install_git "ruby-1.9.3-dev" "https://github.com/ruby/ruby.git" "ruby_1_9_3" autoconf standard