Merge "rust: Allow no_stdlibs per-target variants." into main am: 5ade28cb am: 08fb62b9

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2829091



Change-Id: I986433c3a668338104661132042c895b46faabf2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>