[releng] add gcab

[Frederic Peters <fpeters src gnome org>]

commit f3f40241adee77a0b80efa59fb36eb12753cf8cc
Author: Frédéric Péters <fpeters 0d be>
Date:   Wed Mar 18 20:32:43 2015 +0100

    add gcab

 tools/smoketesting/tarball-conversion.config |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/tools/smoketesting/tarball-conversion.config b/tools/smoketesting/tarball-conversion.config
index c1b0303..c17a528 100644
--- a/tools/smoketesting/tarball-conversion.config
+++ b/tools/smoketesting/tarball-conversion.config
@@ -267,6 +267,7 @@
     <package name="vinagre"                     set="apps"/>
 
     ## TESTED APPS DEPENDENCIES
+    <package name="gcab"/>
     <package name="appstream-glib"/>
     <package name="gdl"/>
     <package name="gdlmm"/>