These only show up post-merge as we're only running ASan there.
This disables the recent `[[clang::preserve_none]]` optimization when
ASan is enabled as there is an LLVM bug on AArch64 that causes register
corruption with that calling convention. This is factored into a common
helper library so we can use it in other places as well.
Assisted-by: Antigravity with Gemini
