Gabriele Renzi points out the latest development in Ruby 2.0:
Sasada Koichi just released YARV 0.3, merged with ruby-head and available as a single download with included ruby sources.
Emphasis mine. No need to patch Ruby HEAD yourself. You’re just a few paragraphs away from having your own little VM by your side. Keep in mind that this only builds miniruby, so we’re sort of still in the first trimester on this one.