[clang] [Clang] Fixed UnresolvedLookupExpr propagating into the codegen phase (PR #124609)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

I'm going to give a conditional approval.  My comfort level is reasonable right now, but I want time to think about it.  So if I haven't responded by ~EOD Monday (or if no one else did other comments), feel free to merge.

https://github.com/llvm/llvm-project/pull/124609