Fixes last remaining failure with test:mri:jit.
This also includes basic functionality for .class output, but it does not generate main or load methods for JRuby 1.7-style AOT.
Unfortunately the many specs that re-spawn JRuby are now causing the build to time out. We have work to do on speeding up boot time for 9k, but right now we need to get green spec runs on travis. We can also set up longer test runs on our Jenkins instance. That may be more appropriate for the long-running suites.