Given ARM_MESI_THREE_Level_HTM is a superset of ARM, it is logical to compile it with clang and with 'fast' compiler optimizations when checking for errors. This increases our test coverage Change-Id: I320291cd543e5db8f543edd81facc91f3f52e17b Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38315 Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu> Tested-by: kokoro <noreply+kokoro@google.com>