Ensure that compiled war file is compiled with the right Ruby version

We currently compile and deploy war files using jruby-1.6.7 in 1.9 mode and found that compile option in warbler was causing compilation to occur in 1.8 mode regardless of flag set in jruby or in warble.rb config.

This might only occur when invoking jruby using 'java -jar jruby-complete-x.x.x.jar' rather than from the exploded jruby distribution (which uses a wrapper script to invoke jruby and jrubyc).