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

[sbence92 at gmail dot com]

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

--- Comment #14 from Bence Szabó <sbence92 at gmail dot com> ---
(In reply to Jakub Jelinek from comment #13)
> Completely untested WIP patch:

Results with ead1c27a530 + this patch:
The same tests fail as in the original description, t032 and t059 crash/pass
the same way as described in comment 6. Also, running the testsuite (check-c++)
shows new failed tests:
FAIL: g++.dg/compat/abi/pr83487-1 cp_compat_x_tst.o-cp_compat_y_tst.o execute
FAIL: g++.dg/compat/abi/pr83487-2 cp_compat_x_tst.o-cp_compat_y_tst.o execute
FAIL: g++.dg/lookup/ns1.C  -std=c++98 (test for excess errors)
FAIL: g++.dg/torture/pr39417.C   -O0  execution test
FAIL: g++.old-deja/g++.robertl/eb21.C  -std=c++14 execution test (timeout)
FAIL: g++.old-deja/g++.robertl/eb21.C  -std=c++17 execution test (timeout)
FAIL: g++.old-deja/g++.robertl/eb21.C  -std=c++2a execution test (timeout)