Share srcs in rust_defaults. am: ad1f4a661c am: 7b308b39c9 am: 0b14238bc3

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rustc-hash/+/1366081

Change-Id: Ieb5b0f5bcbb3bd3ebb046eabe976f7a442b1c055