Merge "Default to Android prebuilt Rust toolchain rather than local toolchain." into main am: 26c05cc107

Original change: https://android-review.googlesource.com/c/platform/development/+/2796405

Change-Id: Ic4a5bf3d4865d4483fc4107c247ba4e6f792b262
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>