[clang] [clang] Fix sorting header paths (PR #73323)

[Tulio Magno Quites Machado Filho via cfe-commits]

tuliom wrote:

> So what breakage is caused by the sorting failure?

@dwblaikie This is not causing a breakage. It is just not working as designed because the sort function has been comparing `""` against `""` since commit https://github.com/llvm/llvm-project/commit/e6830b6028ec5434ccf8dbebdd992918f67b1751 .

I found this while investigating issue #73145.

The way the code is behaving now, the sort function is acting as a NOP and could be removed. However, I don't think that was the intention of the author of https://github.com/llvm/llvm-project/commit/7ff29148ac7883881e62dc9e1714057c68ad4436.

> Can that behavior be tested in some way to validate this change and ensure it doesn't regress in the future?

Possibly. Let me think on this.

https://github.com/llvm/llvm-project/pull/73323