Add a -build-checksum flag to bcc

bug 19216507

Add a flag to bcc to pass a build checksum.  The checksum is passed to
RSEmbedInfo pass via LLVM metadata.

The old checksum path is tied to RSInfo.  Removing this path can be done
along with RSInfo removal.

Change-Id: I3f21c96ddcfe42c16754fbb7749a72595f90964d
9 files changed