Merge "Revert^2 "Remove external/libcxxabi in favor of prebuilt"" into main am: e531c5bd72 am: fa41ef6f0c

Original change: https://android-review.googlesource.com/c/platform/external/libcxxabi/+/3073093

Change-Id: Icf0c5038ae813b64166498a2b8d1a46178500a45
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>