[gnome-robots] Try to fix the flatpak build

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 35fb4e048d08e2ff4f5d84f8e561cf3506177714
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri Jan 3 20:21:33 2020 -0600

    Try to fix the flatpak build

 build-aux/org.gnome.Robots.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/build-aux/org.gnome.Robots.json b/build-aux/org.gnome.Robots.json
index 7a3ddd4..1c42c9f 100644
--- a/build-aux/org.gnome.Robots.json
+++ b/build-aux/org.gnome.Robots.json
@@ -26,6 +26,7 @@
     ],
     "modules": [{
             "name": "libgnome-games-support",
+            "buildsystem": "meson",
             "modules": [{
                     "name": "libgee",
                     "config-opts": ["--enable-introspection=no"],