[clang] [clang] Fix sorting module headers (PR #73146)

[Tulio Magno Quites Machado Filho via cfe-commits]

tuliom wrote:

> Sorry, I don't quite understand tnhis - but I guess the second field ( PathRelativeToRootModuleDirectory ) comparison was to address this bug?

@dwblaikie Yes.

> It'd probably be good to fix that separately, so it can be discussed in more detail, etc.

The commit is already very small. Splitting it wouldn't help with bisect, as we would continue having a broken commit. After the both issues are understood, it becomes easy to understand why they're being made.
If you have more questions that would help you understand this commit, I'd be glad to answer them.

https://github.com/llvm/llvm-project/pull/73146