Android mainline 12.0.0 release 2
Generate apex_available from c2a instead of a patch am: 6e21a92345 am: b9ecefff4f am: 33e398951a am: 714e5c0e39

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures/+/1688688

Change-Id: I35128b69f19f61b3df5e048e60d7d7b9580ea630