Take libcore off the LP64 blacklist.

Change-Id: I34bc49370ecdd37f83927c3829c775e404bcbd73
Generate .pb.cc/.pb.h to arch-neutral generated_sources_dir

So a library can export the proto's include path that can be used with
both archs in multilib build.

Change-Id: Ia0f92f0b40e39dc3fa426c69c52139a0a8f04077
Merge "Generate .pb.cc/.pb.h to arch-neutral generated_sources_dir"
Merge "Take libcore off the LP64 blacklist."
Merge remote-tracking branch 'origin/master'