Starlark-based product configuration can now share version settings
with makefile product config (mk2rbc converts version_defaults.mk into
version_defaults.rbc which is consumed by runtime initialization).
Bug: 198995713
Test: rbcrun build/make/tests/run.rbc
Change-Id: I1d3ddfed3b15d346b3e10714a195a9f0a3a55a56
