Merge "linux_bionic_arm64 is always built from source" am: d48ce92368 am: b0123fa280 am: 1d0eff3aae

Original change: https://android-review.googlesource.com/c/platform/external/llvm/+/1409867

Change-Id: I6d640b44913272c6a1dd8914f69d659dcfb7f79c