Fix tests

So all these years I was totally deluded about the meaning of "set
-e". You might think that it causes statements like "false && true" or
"! true" to fail, but it doesn't...

tests/build-hook.hook.sh

@@ -20,4 +20,4 @@ while read x y drv rest; do
         echo "# decline" >&2
     fi
 
-done
+done