Merge "Factor libc++_host use into llvm_host_defaults" into main am: 330f2f716b

Original change: https://android-review.googlesource.com/c/platform/development/+/2676417

Change-Id: I188b4195fc7399f56b8da60bfecf92f3972a72eb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>