I am running within a Ruby script (a Vagrantfile, specifically) and I want to invoke another ruby executable (berks installed against system ruby, specifically). I know I can do something like
PATH=/usr/bin GEM_PATH=/var/lib/ruby/1.9.1 berks ...
But, that's not very portable. (Different machines will need different GEM_PATH, for instance). So, how can I invoke a script installed against a different Ruby environment from within a Ruby script?