Handle cl.exe specific arguments to zig cc with --driver-mode=cl

[Sahnvour]

As discussed on IRC, it might be mandatory to support cl.exe-style arguments to clang via zig cc.
We could use --driver-mode=cl to accept specific flags like /Z7 to generate PDB files, and -Xclang to pass classic-style arguments.

[andrewrk]

The problem here is trying to enable PDB debugging when compiling C code right? And for some reason clang is rejecting certain arguments? Sounds like an upstream bug report is in order, yeah?

[Sahnvour]

I'd have to do a more thorough test first but yes, that came from the observation that C object files built by zig probably have no debug info, as they were shown ??? in stack traces.