Meson: Build fam module

gio-querymodules-wrapper.py is copied from glib-networking. This python
wrapper script is needed because meson.build cannot check for DESTDIR
env variable itself, unlike Makefile.am. It is used to update
giomodule.cache file when installing GIO modules like fam.

gio/gio-querymodules-wrapper.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python3
+
+import os
+import subprocess
+import sys
+
+if not os.environ.get('DESTDIR'):
+  print('GIO module cache creation...')
+  subprocess.call([sys.argv[1], sys.argv[2]])