Merge "libc: point some x86_64 function impls at llvm-libc" into main am: ed6573b5c4

Original change: https://android-review.googlesource.com/c/platform/bionic/+/3324477

Change-Id: Iebe111f2dcaeff4ac7a81364f71e2771dbe2fd2f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>