clang-check(tools): exit when set illegal option

and not when pass -c parameter, it is break some part of gitlab-ci (Clang Builder)

tools/validate-clang-check.sh

@@ -18,10 +18,10 @@ do
     case $OPTCHAR in
     c)
         CLANG_CHECK_CMD="clang-check-$OPTARG"
-        exit 0
         ;;
     *)
         echo "Usage: $( basename "$0" ) [ -c <clang version> ]"
+        exit 0
     esac
 done