[clang] [clang] Reject invalid record declarations in builtin bit_cast checks (PR #235341)

[Daniel Petrovic via cfe-commits]

daniel-petrovic wrote:

> I wonder if instead we should have an early return on `T->isIncompleteType()`

Thanks for the hint. Will take a look. 

https://github.com/llvm/llvm-project/pull/235341