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

[Sharadh Rajaraman via cfe-commits]

sharadhr wrote:

The Linux tests that failed nearly instantaneously seem to have failed because of a CI permissions issue and are hence irrelevant. There are more critical Windows/macOS failures that have to do with PCHs when running with `clang-cl`, and I shall investigate them. 

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