-march=armv8-a+crc+crypto detected as "yes" on ppc64 clang

[luke-jr]

Building with clang for ppc64, configure detects

checking whether C++ compiler accepts -march=armv8-a+crc+crypto... yes

But the following intrinsic checks still fail, so this is mostly harmless.

Upstream LLVM issue: llvm/llvm-project#57587

[fanquake]

Going to close this for now, as there isn't really anything here for us to do. Upstream now has a change open to fix the problem: https://reviews.llvm.org/D145141, that should land in LLVM/Clang 17.x.