init: complain on unrecognized option with builtin getopt_long_only()

It returns '?' for a bad option, whereas the glibc one does
not. Catch that so we behave identically.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/init.c b/init.c
index d22ed5f..fca74fe 100644
--- a/init.c
+++ b/init.c
@@ -1641,6 +1641,9 @@
 			do_exit++;
 			exit_val = fio_monotonic_clocktest();
 			break;
+		case '?':
+			log_err("%s: unrecognized option '%s'\n", argv[0],
+							argv[optind - 1]);
 		default:
 			do_exit++;
 			exit_val = 1;