To make Sublime Text use chruby's default Ruby version, modify ~/Library/Application\ Support/Sublime\ Text\ 2/Packages/Ruby/Ruby.sublime-build to look like this:

{ "env": { "PATH":"/usr/local/bin/:${PATH}" },	"cmd": ["chruby-exec", "ruby", "--", "ruby", "$file"],	"file_regex": "^(...*?):([0-9]*):?([0-9]*)",	"selector": "source.ruby" } 

To differentiate the name of this build from the default system one, the file can be optionally renamed to ChRuby.sublime-build.