[llvm] [Utils] fix diff_test_updater on Windows (PR #158235)

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dyung wrote:

> > Can you take a look?
> 
> Was asleep, sorry! But I see you fixed it with the mismatching CRs, thanks. Not sure why that didn't end up being an issue on my Windows machine; I don't use Windows very often, but I would've expected it to behave consistently.

No worries, I figured as much when you did not respond and decided to take a look.

How are you running the tests on your Windows machine? If inside WSL, that might be the reason why.

https://github.com/llvm/llvm-project/pull/158235