Adding '_nostd' variant for ring crate. am: 630e65a949

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/ring/+/2797497

Change-Id: I58d4f8486c6871685a9f24b1d0bee36178f44e48
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>