Forget what you read here before, and just do the following:
curl -O http://files.rubyforge.vm.bytemark.co.uk/ruby-debug19/linecache19-0.5.13.gem
curl -O http://files.rubyforge.vm.bytemark.co.uk/ruby-debug19/ruby-debug-base19-0.11.26.gem
gem install {linecache19-0.5.13.gem,ruby-debug-base19-0.11.26.gem} \
-- --with-ruby-include=$rvm_path/src/`rvm current | sed 's/@.*//'`
Or, if you do vendor your gems with bundler, use the following:
curl http://files.rubyforge.vm.bytemark.co.uk/ruby-debug19/linecache19-0.5.13.gem \
> vendor/cache/linecache19-0.5.13.gem
curl http://files.rubyforge.vm.bytemark.co.uk/ruby-debug19/ruby-debug-base19-0.11.26.gem \
> vendor/cache/ruby-debug-base19-0.11.26.gem
bundle config build.ruby-debug-base19 \
--with-ruby-include=$rvm_path/src/`rvm current | sed 's/@.*//'`
You can also find this as a gist.