Usage function called wrong in nc-config

`usage` needs to be called with an exit value. Incorrect options won't
set the exit value, so are trickier to detect

nc-config.cmake.in

@@ -350,9 +350,8 @@ while test $# -gt 0; do
 
     *)
         echo "unknown option: $1"
-	usage
-	exit 1
-	;;
+	    usage 1
+	    ;;
     esac
     shift
 done

nc-config.in

@@ -297,9 +297,8 @@ while test $# -gt 0; do
 
     *)
         echo "unknown option: $1"
-	usage
-	exit 1
-	;;
+	    usage 1
+	    ;;
     esac
     shift
 done