LLVM cttz.v8i8 intrinsic broken on AArch64

[TheIronBorn]

[ui]8x8::trailing_zeros will need a workaround until fixed.

Reported to LLVM: https://bugs.llvm.org/show_bug.cgi?id=39729

[nikic]

Fixed upstream, llvm/llvm-project@a3be17e in monorepo.

[moshg]

Just for my curiosity, why this and #193 are not closed?

[gnzlbg]

Nobody has verified that the fix actually fixed the issue yet.