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

[David Spickett via cfe-commits]

DavidSpickett wrote:

Thanks for confirming, yes, your patch is working as expected but something about Windows' output is tripping up FileCheck I think.

Linux does not print the `clang-repl>` (maybe because it can tell it's outputting to a non-interactive pipe):
```
$ cat ../llvm-project/clang/test/Interpreter/lambda.cpp | ./bin/clang-repl -Xcc -Xclang -Xcc -verify -Xcc -O2
ONE
TWO
TWO
error: Parsing failed.
x = 42
```
Which should not be a problem in theory.

I'll will figure it out.

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