Merge "rust: Allow no_stdlibs per-target variants." into main am: 5ade28cb am: 177724f1

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



Change-Id: I9c33a4943caea445869c5cb19efa0394adf7457f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>