[clang] Add option -fstdlib-hardening= (PR #78763)

[Sam James via cfe-commits]

thesamesam wrote:

> No other thoughts for now. GCC has `-fhardened` now, which already defines that macro. This seems kinda redundant with it.

Yes, please, unless there's a strong reason not to, consider `-fhardened`. Otherwise we may as well just be telling people to set `-D...` themselves.


https://github.com/llvm/llvm-project/pull/78763