This MR is opened to improve the status of the Visual Studio builds done with Meson, as well as fixing and enhancing builds with distutils:
For both build systems:
-Force-include msvc_recommended_pragmas.h (which is part of GLib on Windows builds), which covers the compile-time flags that we want to look out for on Visual Studio builds
-Update pygi-closure.c to avoid compiler errors (which is raised with C4047, which we are wary about) by just casting arg->v_pointer to ffi_arg (which is more-or-less like a void pointer).
-Manully look for Cairo and Cairo-GObject on Visual Studio builds, if their pkg-config files could not be found, because the Makefiles shipped with Cairo do not generate pkg-config files for us.
-Fix the build on Visual Studio, since the distutils compiler instance is different on Visual Studio (no compiler sub-attribute).
-Enable tests to build and run on Visual Studio builds as well.
This is also likely needed for the Master branch.
With blessings, thank you!