[automerger skipped] [DO NOT MERGE] Add RBE mk file to support bootstrapping...

[automerger skipped] [DO NOT MERGE] Add RBE mk file to support bootstrapping RBE and setting relevant am: 7298be1b am: edd7e730 -s ours am: 428006cf -s ours

am skip reason: Change-Id Ifb6bfd9f7292346f4750a6a409aa0def4e3c0363 with SHA-1 ec8b8dfa is in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/12468471

Change-Id: I8fbf4b398486f432d88031e5a7834c9528d86ac0