Add java_genrules to use jars as inputs and outputs

Add a java_genrule that has the right multilib flags to be a
dependency of a java rule.  Make java libraries implement
SourceFileProducer so that their classes jar can be used as an
input to a java_genrule.  Allow libs and static_libs dependencies
to be a java_genrule.

Test: TestJarGenrules
Change-Id: Ib1b31ef9c0b7e72eeed2c9ecc4ce8a1088e0b1c9