--with-system-glib for mingw

After 047bc546 it is no longer triggered
by rsvg alone, so I guess this is the right way to get system glib on migw again.

distro-configs/LibreOfficeMinGW.conf

@@ -8,6 +8,7 @@
 --with-system-db
 --with-system-expat
 --with-system-gettext
+--with-system-glib
 --with-system-graphite
 --with-system-hunspell
 --with-system-icu