The position of first argument to check from is 6, not 0.
Looks like our tests with CFORMAT was simply not working
since commit 7d12d66e (Refactor macroses for compiler
builtins and function attributes).

Lets turn them all back.

Follow-up #5846

Reported-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>