Merge "Set ALLOW_UNKNOWN_WARNING_OPTION" am: 5a5aa3357a

Original change: https://android-review.googlesource.com/c/platform/development/+/2161662

Change-Id: If7f0dd37bed7d027c3aecee9c20fd3426de8b8b7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>