git clone https://github.com/cldwalker/debugger-ruby_core_source.git
cd debugger-ruby_core_source.git
gem install archive-tar-minitar
VERSION=2.0.0-p594 rake add_source
gem install debugger -- --version '1.6.8' --with-ruby-include=/../../debugger-ruby_core_source/lib/debugger/ruby_core_source/ruby-2.0.0-p594