[clang] [clang][CodeGen] Keep processing the rest of AST after encountering unsupported MC/DC expressions (PR #82464)

[Alan Phipps via cfe-commits]

https://github.com/evodius96 approved this pull request.

LGTM. thanks for catching and fixing this.  Would also be good to get this onto 18.x if possible.

https://github.com/llvm/llvm-project/pull/82464