Add build files for strum_macros crate am: 4a20de7f76

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/strum_macros/+/2924633

Change-Id: If2e2a47130df32674835b683f79e73927ea427b8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>