[pitivi] flatpak: Pass GTK_THEME to the sandboxed Pitivi when developing

[Alexandru Băluț <alexbalut src gnome org>]

commit 7706e9b3301d1c22cef50d725fb6cd0b3d4a9e11
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Mon Oct 3 09:45:39 2016 +0200

    flatpak: Pass GTK_THEME to the sandboxed Pitivi when developing

 build/flatpak/pitivi-flatpak |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/build/flatpak/pitivi-flatpak b/build/flatpak/pitivi-flatpak
index 3809f97..76266e7 100755
--- a/build/flatpak/pitivi-flatpak
+++ b/build/flatpak/pitivi-flatpak
@@ -530,6 +530,7 @@ class PitiviFlatpak:  # pylint: disable=too-many-instance-attributes
                 "GST_VALIDATE",
                 "GST_VALIDATE_LAUNCHER_DEBUG",
                 "GTK_DEBUG",
+                "GTK_THEME",
                 "LANG",
                 "PITIVI_DEBUG",
                 "PITIVI_DEVELOPMENT"]: