build: Drop nmake/MSC build system for GLib

It hasn’t been seriously maintained for the best part of 10 years and is
very outdated. The recommended way to build GLib on Windows is now
Visual Studio:

https://wiki.gnome.org/Projects/GTK%2B/Win32/MSVCCompilationOfGTKStack#GLib



Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=722047