[clang] [compiler-rt] [SafeStack] Introduce public interface header and deprecate builtins (PR #198292)

[Jakob Koschel via cfe-commits]

jakos-sec wrote:

> > I've added __safestack_get_unsafe_stack_ptr in this commit and it's only used in a test. There shouldn't be any other use of it in the backend, if I'm not mistaken.
> 
> Oh, hmm, I think I got confused looking at SafeStack.cpp. There is a function `__safestack_pointer_address`, but I guess that isn't quite the same thing?

Ah yes, that one is actually used by the compiler and the pass itself (although disabled by default), but is fully unrelated to the new `__safestack_*` diagnostic based functions. Good point though!

https://github.com/llvm/llvm-project/pull/198292