[gjs] build: Require GTK 3.20

[Philip Chimento <pchimento src gnome org>]

commit 62e255bc51416bbce107c36be9e86a09a6c3de0f
Author: Philip Chimento <philip chimento gmail com>
Date:   Sat Sep 3 12:52:36 2016 -0700

    build: Require GTK 3.20
    
    Our Gtk.WidgetClass now requires gtk_widget_class_set_css_name(), which
    was first available in 3.20.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=742249

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 49b0cb3..f1eb107 100644
--- a/configure.ac
+++ b/configure.ac
@@ -79,7 +79,7 @@ common_packages="gmodule-2.0 gthread-2.0 gio-2.0 >= glib_required_version mozjs-
 gjs_packages="gobject-introspection-1.0 libffi $common_packages"
 gjs_cairo_packages="cairo cairo-gobject $common_packages"
 gjs_gdbus_packages="gobject-2.0 >= glib_required_version gio-2.0"
-gjs_gtk_packages="gtk+-3.0"
+gjs_gtk_packages="gtk+-3.0 >= 3.20"
 # gjs-tests links against everything
 gjstests_packages="gio-unix-2.0 $gjs_packages"