2814dfa does break jruby-complete.jar - see http://ci.jruby.org/job/jruby-dist-master/1901/console
reverting the commit fixes it locally. you can test it by running
$ mvn clean install -Pcomplete
the complete jar build has some integration tests (ITs) which uses the jruby-complete.jar to run some basic tests.
same error is the on jruby-1_7 branch as well
Fixed in a recent commit. We had a endless loop asking for global runtime to ask for Jar which would create a global runtime which would create a global runtime ....