[gnome-screenshot] flatpak: Specify builddir: true for the last module

[Alexander Mikhaylenko <alexm src gnome org>]

commit 67ac52eca5718b086411823ca9649ecd0c6ca4f4
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Mar 10 01:48:43 2020 +0500

    flatpak: Specify builddir: true for the last module
    
    This pleases Builder so it doesn't create `_build` dir.

 org.gnome.Screenshot.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/org.gnome.Screenshot.json b/org.gnome.Screenshot.json
index fce322a..ecd27d1 100644
--- a/org.gnome.Screenshot.json
+++ b/org.gnome.Screenshot.json
@@ -53,6 +53,7 @@
         {
             "name" : "gnome-screenshot",
             "buildsystem" : "meson",
+            "builddir" : true,
             "sources" : [
                 {
                     "type" : "git",