[llvm] [MC] Fix DWARF file table for files with empty DWARF (#119020) (PR #119229)

[Aleksei Vetrov via llvm-commits]

noxwell wrote:

> This causes emitting .debug_line w/o any dwarf options in clang %.S. Is it desired?

Yes, it needs a check `if (getContext().getGenDwarfForAssembly())`, which I forgot. I don't think I have rollback permissions, could anyone do it for me? Or I can bring fix forward tomorrow.

https://github.com/llvm/llvm-project/pull/119229