[clang] [Clang] Fix assertion failure in getASTRecordLayout for invalid declarations (PR #208153)

[Erich Keane via cfe-commits]

erichkeane wrote:

I don't think this is the rightway to recover from this error.  We need to figure out how we got here and escape.  I wonder if instead of keying the 'entry' list to the declaration in this case, we should just store a "invalid-decl-layout".

Though, I'm reasonably unconvinced this will be right, since users of the layout are often going to check for a field being in the ASTLayout that they know SHOULD be, and the 'fake' one won't have them.

https://github.com/llvm/llvm-project/pull/208153