[clang] [clang-repl] Fix error recovery while PTU cleanup (PR #127467)

[David Spickett via cfe-commits]

DavidSpickett wrote:

I've disabled the failing `RUN` line on Windows and opened https://github.com/llvm/llvm-project/issues/143547 with details of what's happening.

Let me know if anything stands out to you. Also would be useful if I can see the code produced at the different optimisation levels.

https://github.com/llvm/llvm-project/pull/127467