[Linkerwrapper] Make -Xoffload-linker pass directly to `clang`

Summary:
We provide `-Xoffload-linker` to pass arguments directly to the link
step. Currently this uses `-Wl,` implicitly which prevents us from using
clang options that we otherwise could make use of. This patch removes
that implicit behavior as users can just as easiliy pass
`-Xoffload-linker -Wl,-foo` if needed.