[llvm] [CMake][Windows] Fix Debug config build when using MSBuild (PR #111765)

[via llvm-commits]

wjristow wrote:

Hi @chapuni,  Does my [explanation above](https://github.com/llvm/llvm-project/pull/111765#issuecomment-2415609507), and [updated approach](https://github.com/llvm/llvm-project/pull/111765#issuecomment-2418787793) make sense to you?  From what I understand, my proposed change is generalizing the change that you made in 95d4506dda79d49e55fdd0e4da7bf81487167aa1, so it seems sensible to me.

But as I said earlier:

> I also want to let you know that I don't have much experience with CMake, so I may be approaching this the wrong way (and so I can abandon this, if that is your opinion after I explain more).

So if you see a better solution, or a way for me to avoid the problem, please let me know.

https://github.com/llvm/llvm-project/pull/111765