This fixes GCC12 warnings about accessing a too small object.

    wine/dlls/msvcrt/tests/cpp.c: In function 'test_rtti':
    wine/dlls/msvcrt/tests/cpp.c:1036:45: warning: array subscript 2 is outside array bounds of 'void[4]' [-Warray-bounds]
     1036 |       ok (casted == (char*)&child_class_sig0+8, "failed cast to simple_class (%p %p)\n", casted, &child_class_sig0);
          |                     ~~~~~~~~~~~~~~~~~~~~~~~~^~
Signed-off-by: Piotr Caban <piotr.caban@codeweavers.com>
Signed-off-by: Eric Pouech <eric.pouech@gmail.com>