windows: Make --pkg-config do nothing on Windows
windows: Make --pkg-config do nothing on Windows

The pkg-config stuff is problematic because it uses Process which
we don't have on Windows.  But it likely won't work right anyway,
since I doubt pkg-config is a thing for native Windows/MSVC builds.
Just skip it when on Windows.

AbePralle/Rogue,Plasmaworks/Rogue,Plasmaworks/Rogue,Plasmaworks/Rogue,AbePralle/Rogue,Plasmaworks/Rogue