[gnome-games] flatpak: Use add-extensions instead of --extension

[Alexander Mikhaylenko <alexm src gnome org>]

commit bd3823e9638c0d91baec5ceae4016b81c1299226
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Fri Feb 7 00:52:32 2020 +0500

    flatpak: Use add-extensions instead of --extension
    
    Mirror a change from flathub.

 flatpak/org.gnome.Games.json | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/flatpak/org.gnome.Games.json b/flatpak/org.gnome.Games.json
index a9b565d1..0c4462bc 100644
--- a/flatpak/org.gnome.Games.json
+++ b/flatpak/org.gnome.Games.json
@@ -11,9 +11,6 @@
     ],
     "desktop-file-name-suffix" : " (Development)",
     "finish-args" : [
-        /* Extension point */
-        "--extension=org.gnome.Games.LibretroPlugin=directory=lib/libretro/extra.d",
-        "--extension=org.gnome.Games.LibretroPlugin=subdirectories",
         /* X11 + XShm access */
         "--share=ipc",
         "--socket=x11",
@@ -39,6 +36,15 @@
         /* Settings migration */
         "--metadata=X-DConf=migrate-path=/org/gnome/Games/"
     ],
+    "add-extensions": {
+        "org.gnome.Games.LibretroPlugin": {
+            "version": "stable",
+            "directory": "lib/libretro/extra.d",
+            "subdirectories": true,
+            "no-autodownload": true,
+            "autodelete": true
+        }
+    },
     "cleanup" : [
         "/include",
         "/lib/pkgconfig",