getconf: fail if any other flag than -v is used

Signed-off-by: Mattias Andrée <maandree@kth.se>
diff --git a/getconf.c b/getconf.c
index e611659..d927f2d 100644
--- a/getconf.c
+++ b/getconf.c
@@ -33,6 +33,9 @@
 		/* ignore */
 		EARGF(usage());
 		break;
+	default:
+		usage();
+		break;
 	} ARGEND
 
 	if (argc == 1) {