Require at least 3.21.3 for the MRU input source schema.
https://bugzilla.gnome.org/show_bug.cgi?id=768956
PKG_CHECK_MODULES(SHELL_HOTPLUG_SNIFFER, gio-2.0 gdk-pixbuf-2.0)
PKG_CHECK_MODULES(TRAY, mutter-clutter-1.0 gtk+-3.0)
PKG_CHECK_MODULES(GVC, libpulse >= $PULSE_MIN_VERS libpulse-mainloop-glib gobject-2.0)
-PKG_CHECK_MODULES(DESKTOP_SCHEMAS, gsettings-desktop-schemas >= 3.21.2)
+PKG_CHECK_MODULES(DESKTOP_SCHEMAS, gsettings-desktop-schemas >= 3.21.3)
AC_ARG_ENABLE(browser-plugin,
[AS_HELP_STRING([--enable-browser-plugin],