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

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

Change-Id: I91c278b133cd4da83f71fca08f41ab26a5b3b002
Signed-off-by: Automerger Merge Worker <[email protected]>