CI: Exit on failure in update-ref.sh

If any part of the script failed, it would silently ignore it.
These bash options will make it fail on the first error and print
the commands as they are executed.

scripts/update-ref.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/bash -ex
 
 # Update the fetch-poky.sh script
 FILE="scripts/fetch-poky.sh"