[clang] [UBSAN] [NFC] add coverage for null and alignment checks (PR #176210)

[Justin Stitt via cfe-commits]

JustinStitt wrote:

I am also a bit confused about what your test is checking. Is it verifying the lack of support from the `null` and `aligned` sanitizers? I see very few `CHECK` lines looking for sanitizer intrinsics, just a bunch of memcpy ops which are emitted even when the sanitizers are off.

https://github.com/llvm/llvm-project/pull/176210