[gnome-music] flatpak: Set build system to "meson"

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 6c1d9b88232d73d10abd9820b6d51438558f2835
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Thu Mar 1 11:19:32 2018 -0300

    flatpak: Set build system to "meson"
    
    So that flatpak-builder can pick the right build system.

 org.gnome.Music.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/org.gnome.Music.json b/org.gnome.Music.json
index 4e16ea0..780dc05 100644
--- a/org.gnome.Music.json
+++ b/org.gnome.Music.json
@@ -169,6 +169,7 @@
         },
         {
             "name": "gnome-music",
+            "buildsystem": "meson",
             "sources": [
                 {
                     "type": "git",