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

[Hans Wennborg via cfe-commits]

zmodem wrote:

> I think '/Fo' is basically '-o'. Its semantic is to specify the path to the output file.

No, `/Fo` is for object files, `/Fe` for the executable, `/Fp` for pch file etc.

> So if now clang-cl can accept '-o' [...]

It works in general in clang-cl. I guess we'd have to double check if it works in the modules use case. And `-fmodule-output` is exposed in clang-cl as well, so it sounds like there are plenty of flags already :)

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