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

[Louis Dionne via cfe-commits]

https://github.com/ldionne commented:

This is nice!

Tagging a few people who might have opinions on the naming: @nico @kubamracek @AaronBallman

Also, @jwakely it would be nice if this worked with libstdc++ as well in the future -- it would probably turn on checks like `__GLIBCXX_ASSERT__`. Do you have thoughts on this? And if we want to do this, then `gcc` would also need to gain an option that works similarly.

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