Migrate to cargo_embargo. am: 4e010678ac am: 783eb19e49

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/num_cpus/+/2838081

Change-Id: I15e755e40d00fd8707cd9af367579613eda7a246
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>