meson: fix static build under Windows

Properly define GLIB/GOBJECT_STATIC_COMPILATION when static build is enabled.
Use library() instead of shared_library() to allow selecting static builds.

https://bugzilla.gnome.org/show_bug.cgi?id=784995

gobject/meson.build

@@ -61,7 +61,7 @@ else
   gobject_dtrace_hdr = []
 endif
 
-libgobject = shared_library('gobject-2.0',
+libgobject = library('gobject-2.0',
   gobject_dtrace_obj, gobject_dtrace_hdr,
   sources : gobject_sources,
   version : library_version,