abuild: abort if payload.sh failed

With this chance it becomes practical to have payload.sh build/update
the payload, and abort abuild if something bad happened.

Change-Id: Iee25de2e8b62153c477b8e5d32e097b59797523c
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/1536
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

util/abuild/abuild

@@ -155,6 +155,10 @@ function create_config
 
 	if [ -f $payloads/payload.sh ]; then
 		PAYLOAD=`sh $payloads/payload.sh $VENDOR $MAINBOARD`
+		if [ $? -gt 0 ]; then
+			echo "problem with payload"
+			exit 1
+		fi
 		printf "Using payload $PAYLOAD\n"
 	fi