[clang] [clang][sema] make sure arguments of __atomic_exchange complete type (PR #75135)

[James Y Knight via cfe-commits]

jyknight wrote:

Why only `__atomic_exchange`? Presumably we need to be doing the same with every other of the atomic builtins as well (unless they already have this check and we only missed it on exchange?)

https://github.com/llvm/llvm-project/pull/75135