[gnome-games] flatpak: Add the Libretro extension point

[Adrien Plazas <aplazas src gnome org>]

commit 7e03afc113ee1f502b859ed8df097e367bde5311
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Mar 8 10:09:02 2017 +0100

    flatpak: Add the Libretro extension point
    
    Add the org.gnome.Games.LibretroPlugin subdirectory-style extensionpoint
    located in /app/lib/libretro/extra.d.
    
    This allows to support Libretro cores as Flatpak extensions.

 flatpak/org.gnome.Games.json |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/flatpak/org.gnome.Games.json b/flatpak/org.gnome.Games.json
index 805f4dd..41000c8 100644
--- a/flatpak/org.gnome.Games.json
+++ b/flatpak/org.gnome.Games.json
@@ -7,6 +7,9 @@
     "tags": ["nightly"],
     "desktop-file-name-prefix": "(Nightly) ",
     "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",
         /* Wayland access */
@@ -126,6 +129,7 @@
         },
         {
             "name": "gnome-games",
+            "post-install": ["mkdir -p /app/lib/libretro/extra.d"],
             "sources": [
                 {
                     "type": "git",