[lld][ELF] Only convert dependency filename to native form on Windows#160927

ZhongRuoyu wants to merge 2 commits intollvm:mainllvm/llvm-project:mainfrom

ZhongRuoyu:lld-dep-filename-backslashesZhongRuoyu/llvm-project:lld-dep-filename-backslashesCopy head branch name to clipboard