[clang] Accept `cl`-style output arguments (`/Fo`, `-Fo`) for `--fmodule-output` (PR #121046)

[Sharadh Rajaraman via cfe-commits]

sharadhr wrote:

> Why is this submitted against the release/19.x branch? Is this a backport? If so, please indicate which commit it backports.

Not a backport but a fix. I have now re-submitted it against `main`, but I'd like it back-ported to `19.x` if possible.

https://github.com/llvm/llvm-project/pull/121046