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

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

Change-Id: Ic11a2321ae4bfc6f9e943fae8a820375181987b7