Generate apex_available from c2a instead of a patch am: d0234f2bbf am: 256379a292 am: 08d47934b0 am: ed39197f07

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/cfg-if/+/1688622

Change-Id: I247e7a2ed4b87422a0bd4c5cdd46d9f1fdfbd40a