Proper cleanup after finishing global-showdef test

The temporary foo directory with classes created by global-showdef.scala was not deleted after finishing a test. When I was running tests from Scala project root, this directory was created there and was visible when running git status.

I just forced the creation of a foo directory inside global-showdef-run.obj - so it's properly deleted after finishing the test.
Okay, so it will be the same as at the beginning. Just the method of getting testOutput will be different (I'm not going to rewrite it to DirectTest or something like that). I'm pushing the new version.