[tali] Try to fix flatpak builds

[Mart Raudsepp <mraudsepp src gnome org>]

commit cb09cfcc8c89f62177bd5d2fa5b3c232a6d91600
Author: Mart Raudsepp <leio gentoo org>
Date:   Sun Apr 26 09:17:07 2020 +0300

    Try to fix flatpak builds

 build-aux/org.gnome.Tali.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/build-aux/org.gnome.Tali.json b/build-aux/org.gnome.Tali.json
index 9cb9c5a..4cb042e 100644
--- a/build-aux/org.gnome.Tali.json
+++ b/build-aux/org.gnome.Tali.json
@@ -39,6 +39,7 @@
         },
         {
             "name": "tali",
+            "buildsystem": "meson",
             "sources": [{
                 "type": "git",
                 "url": "https://gitlab.gnome.org/GNOME/tali.git";