[clang] [Win32][ELF] Make CodeView a DebugInfoFormat only for COFF format (PR #87149)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> I am curious what a `win32-elf` triple is. Does MSVC support generating ELF object files?

No idea, but https://github.com/llvm/llvm-project/issues/87140 doesn't look like from fuzzing.
Consider Windows has WSL now, I'd not surprise it's supported or will be supported someday, see https://learn.microsoft.com/en-us/cpp/build/walkthrough-build-debug-wsl2?view=msvc-170

https://github.com/llvm/llvm-project/pull/87149