[Clang] -Wpsabi complains too eagerly

[philnik777]

Clang currently complains when calling a function that the ABI changes if a feature is enabled, but ignores that the function is marked [[gnu::always_inline]], which ensures that the type will never be part of the ABI. e.g.

using vec [[gnu::vector_size(32)]] = int;

[[gnu::always_inline]] vec test() {
  return {};
}

void call() {
  (void)test(); // complains that test() changes the ABI with avx enabled
}

Ironically, it doesn't complain if the address is taken, which is one of the few cases where this would actually matter, since LLVM might not be able to inline a call to the function pointer.