[gnome-panel] clock: fix build

[Alberts Muktupāvels <muktupavels src gnome org>]

commit a4fd9238833abba871a4da7c3ec9f90b53fb0a57
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Sep 12 19:32:12 2018 +0300

    clock: fix build
    
    https://gitlab.gnome.org/GNOME/gnome-panel/issues/8

 configure.ac | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/configure.ac b/configure.ac
index c13fbdadc..17ae568c1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -196,6 +196,7 @@ AC_CHECK_FUNCS(nl_langinfo)
 PKG_CHECK_MODULES([CLOCK], [
   dconf >= $DCONF_REQUIRED
   gio-2.0 >= $GLIB_REQUIRED
+  gio-unix-2.0 >= $GLIB_REQUIRED
   glib-2.0 >= $GLIB_REQUIRED
   gnome-desktop-3.0 >= $LIBGNOME_DESKTOP_REQUIRED
   gtk+-3.0 >= $GTK_REQUIRED