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

[Oliver Hunt via cfe-commits]

ojhunt wrote:

Ok, so after some investigation, when we construct the invalid record, we do mark it as being invalid, so we can just test for `isInvalidDecl()` when we encounter a record, and that test is transitive over the nested types in the record. 

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