Merge "Turn on LTO for libc++.so" am: 0860713e9e am: 8be550233c am: c29582f711 am: 517c70c1d0 am: 791851c8b5

Original change: https://android-review.googlesource.com/c/platform/external/libcxx/+/2623791

Change-Id: Ib5d1012a0f5a1ec957e49762796492ff4ef5c8e3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>