[clang] [nfc][ubsan] Add local-bounds test (PR #122415)

[Vitaly Buka via cfe-commits]

vitalybuka wrote:

> Would it be useful to keep -fsanitize=...null and add local-bounds instead of replacing null with local-bounds? It would make the test more rigorous and also make the diff smaller.
> 
> **edit:** or is it not possible to make a test case that is local-bounds sanitized where null sanitization does not apply?

Thanks, looks like I failed merge conflict resolution.
Removing null was not an intention.


https://github.com/llvm/llvm-project/pull/122415