[clang] [clang][ARM][AArch64] Reapply "Define intrinsics guarded by __has_builtin on all platforms (#128222)" (PR #140910)

[Nico Weber via cfe-commits]

nico wrote:

> One idea would be to have intrin.h include arm_acle.h, but that would still yield a misleading warning if the user didn't include either.

It'd presumably also be pretty bad for post-preprocessor file size and compile time, right?

https://github.com/llvm/llvm-project/pull/140910