[Bug target/94770] class with empty base passed incorrectly with -std=c++17 on mingw

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94770

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The third __builtin_abort() is called:

  if (__builtin_va_arg (ap, long long) != 2LL)
    __builtin_abort ();