clone.sh: Run with shell tracing

Required to debug https://linaro.atlassian.net/browse/TFC-210, but as any
issue may appear at any time, it should always run like that.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I2a55f883d88f0043d78852d26c4c0d0fc6977eba
diff --git a/clone.sh b/clone.sh
index 7972516..e5d0531 100755
--- a/clone.sh
+++ b/clone.sh
@@ -27,7 +27,7 @@
 # is triggered manually from the buider job itself.
 #
 
-set -e
+set -ex
 
 . $(dirname $0)/util_git.sh