Enable clang to version 9.0. am: acad6360b1 am: 3c954f07fd am: c91e2ccf02

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/clang-sys/+/1350712

Change-Id: I7043b535de53d04486ceb73f59dbe3b40d89c8fc