Support cpp backend for libfmq am: 4d606ccb65

Original change: https://android-review.googlesource.com/c/platform/system/libfmq/+/3364942

Change-Id: I38ccbc0be9c740531a520ae4942473ece3d1124f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>