Update prebuilt Clang to r468909b (15.0.3). am: 8cbc77cf96

Original change: https://android-review.googlesource.com/c/platform/prebuilts/clang/host/darwin-x86/+/2243002

Change-Id: I6b73b1337f0e2f1912de4d0cf4d5bdefad1e5556
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>