Created by: grumpyjames
Summary: We only need to expose the generated source directory (which may not exist). As AnnotationProcessingParams is java specific (rather than jvmlang agnostic) we'd prefer JavaLibrary (soon to become JvmLibrary) to not know about it.
Context: I'm another LMAX person. We really want to make some progress towards the work described in https://github.com/facebook/buck/pull/439
Tested with ant && ./bin/buck test (advice on whether this is enough gratefully received!)