libloading: make libloading vendor available. am: e5afd9f6aa am: 89b02bcdf5 am: 4e06fcb867

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/libloading/+/2457728

Change-Id: I7b9d92692a3d9d402aa917d85255147c124a4acd
Signed-off-by: Automerger Merge Worker <[email protected]>