[clang] [Clang] Assume unaligned in maksed load / store builtins (PR #156063)

[Nikolas Klauser via cfe-commits]

philnik777 wrote:

IMO the right default alignment would be `alignof(*ptr)`. Objects are pretty much never underaligned, but they tend to not be overaliend unless you want something specific - at which point you can use `__builtin_assume_aligned` to inform the compiler that it can use higher alignment assumptions.

https://github.com/llvm/llvm-project/pull/156063