This is an example of how to have a repo version of Ruby 1.8.7, Rake, and Albacore to build your solution. This is useful in scenarios where you cannot or do not want to install Ruby on your build server (how unfortunate!). Ruby and the required components lives in the Tools folder. The build.sh and build.cmd scripts will use this copy of Ruby to clean, build, test, etc your solution based on the tasks defined in rakefile.rb. This example was made possible by looking through the machine.specifications repo, where great things have been created... and caffeine, lots of caffeine.
codereflection/BuildWithRuby
Example of how to build your .net solutions with a repo copy of Rake and Albacore
Ruby