[Bug c/81851] missing -Wduplicated-branches on if and return statements with no else

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81851

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Should it warn here?

int g (int i)
{
  if (i == 0)   // no warning
    return 0;
#if SOME_OTHER_PLATFORM
  if (i == 2)
    return 1;
#endif
  return 0;
}

When not compiling for SOME_OTHER_PLATFORM this ends up being equivalent to
your original g, do you want this to warn?