[llvm] Fix test on Windows by telling diff to ignore Windows-specific line endings. (PR #158297)

[via llvm-commits]

dyung wrote:

The precommit failure is also present in at least one build bot, so is unrelated to this change: https://lab.llvm.org/buildbot/#/builders/195/builds/14511

https://github.com/llvm/llvm-project/pull/158297