[llvm] [lit] Fix lit hang on pool join when exception is thrown (PR #131881)

[David Garcia Orozco via llvm-commits]

ayylol wrote:

> So is this in fact still an issue on 3.8+ and was not fixed there?

Yep, I was able to reproduce the hang on Python 3.12.3

https://github.com/llvm/llvm-project/pull/131881