Merge "rust: Allow rustlibs to fallback to rlibs." am: 3736abfa am: b6289c9b am: 7cf46f00

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2058050



Change-Id: I7582690ae1a14c4b5b2de364acaf94695845815e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>