build: Compile the GSettings schema after installation

Fallout from 10738d68c6

https://gitlab.gnome.org/GNOME/gnome-control-center/issues/8

meson_post_install.py

@@ -4,8 +4,12 @@ import os
 import subprocess
 import sys
 
+gsettingsschemadir = os.path.join(sys.argv[1], 'glib-2.0', 'schemas')
 icondir = os.path.join(sys.argv[1], 'icons', 'hicolor')
 
 if not os.environ.get('DESTDIR'):
+  print('Compiling gsettings schemas...')
+  subprocess.call(['glib-compile-schemas', gsettingsschemadir])
+
   print('Update icon cache...')
   subprocess.call(['gtk-update-icon-cache', '-f', '-t', icondir])