Update prebuilt Clang to r468909 (15.0.2). am: 68749492fd am: 2bf8fe9505

Original change: https://android-review.googlesource.com/c/platform/prebuilts/clang/host/darwin-x86/+/2230860

Change-Id: Ibe895aaa1e78c94d215c83eeee87658fe6536d7f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>