Share srcs in rust_defaults am: 36d7307a9c am: 44365bad88 am: 859eab669b am: 7780ece6df

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/bitflags/+/1365688

Change-Id: Iba4cd12a02bb0fb03d53534e938c7d75339a0244