groovy_library use argfile for list of sources.

Created by: trevorriles

To avoid issues with ARG_MAX limits when running the groovy_library build rule, the groovyc step should work like that javac step by writing a list of sources to file then executing the compiler on those sources.

The javac build step writes a files to buck-out/gen/x/__y__srcs for a build target of //x:y