[clang] [PAC][clang] Correct handling of ptrauth queries of incomplete types (PR #164528)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

@AaronBallman do you have any idea how I might be able to get a field with an invalid or incomplete type without causing the containing record to be marked incomplete or invalid?

https://github.com/llvm/llvm-project/pull/164528