[clang] [clang][Sema] Fix crash on atomic builtins with incomplete type args (PR #96374)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for the fix! The changes should also come with a release note in `clang/docs/ReleaseNotes.rst` so users know about the improvement.

https://github.com/llvm/llvm-project/pull/96374