Merge "Remove external/libcxxabi in favor of prebuilt" into main am: f2044687b7 am: 8c000a48a2

Original change: https://android-review.googlesource.com/c/platform/external/libcxxabi/+/2675522

Change-Id: Id34b9fa106f0e324efaa6e5534983a9d8f2acc8d
Signed-off-by: Automerger Merge Worker <[email protected]>