[llvm] [clang] [X86] Use unaligned atomic load and stores (PR #79191)

[James Y Knight via cfe-commits]

jyknight wrote:

This is incorrect: X86 does not support unaligned atomics.

However, LLVM can codegen correctly for atomics of any alignment in IR, on any architecture (via using libcalls when necessary). So the ObjC code's `hasUnalignedAtomics` could be removed, and let the backend deal with it, if that was desirable.

https://github.com/llvm/llvm-project/pull/79191