[lld] [LLD][COFF] Create COFFObjectFile instance when constructing ObjFile (NFC) (PR #120144)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo approved this pull request.

LGTM - this is kinda complicated, but your explanation sounds reasonable, and I think I've managed to follow it, so this sounds ok to me.

https://github.com/llvm/llvm-project/pull/120144