[automerger skipped] [DO NOT MERGE] Add RBE support for Javac, R8, and D8 if...

[automerger skipped] [DO NOT MERGE] Add RBE support for Javac, R8, and D8 if respective env vars are set. am: c9a030aa am: 5507116c -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/12468474

Change-Id: Ib410589e42eba5eb0cee6e61a52cf8ea30fb771a