[gnome-builder] build: pin amtk to built tarball

[Christian Hergert <chergert src gnome org>]

commit 2cf5b848bc8e2a7f92c1f8c9dfcc44639b885208
Author: Christian Hergert <chergert redhat com>
Date:   Thu Aug 1 16:32:34 2019 -0700

    build: pin amtk to built tarball
    
    These seem to be breaking with dependency tracking in master, so this
    helps get things working further.

 build-aux/flatpak/org.gnome.Builder.json | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/build-aux/flatpak/org.gnome.Builder.json b/build-aux/flatpak/org.gnome.Builder.json
index 99892b49c..a92a9d99c 100644
--- a/build-aux/flatpak/org.gnome.Builder.json
+++ b/build-aux/flatpak/org.gnome.Builder.json
@@ -288,8 +288,9 @@
             "builddir" : true,
             "sources" : [
                 {
-                    "type" : "git",
-                    "url" : "https://gitlab.gnome.org/GNOME/amtk.git";
+                    "type" : "archive",
+                    "url" : "https://download.gnome.org/sources/amtk/5.0/amtk-5.0.0.tar.xz";,
+                    "sha256" : "12a996978a30b7b69a810ac0c5656d5cf2f58d9787b98a0c028ff1b64e8f31ff"
                 }
             ]
         },