add update_sbuild helper

diff --git a/update_sbuild b/update_sbuild
new file mode 100755 (executable)
index 0000000..f2a415a
--- /dev/null
+++ b/update_sbuild
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+schroot -l |awk -F: '/^source/{print $2}'|xargs -d '\n' sudo sbuild-update -udcar;