[clang] [LinkerWrapper] Fix `-Xoffload-linker a=b` in offloading (PR #100270)

[Shilei Tian via cfe-commits]

https://github.com/shiltian commented:

I think LLVM generally doesn't follow the convention that `-a x` and `--abc=x`?

https://github.com/llvm/llvm-project/pull/100270