Merge "Default to Android prebuilt Rust toolchain rather than local toolchain." into main am: 26c05cc107 am: 18abed74f7

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

Change-Id: I0d6050c85102d958d62be12c8e8c9d1912b29ead
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>