Do I understand correctly that the problem with this patch is that it adds -mpreferred-stack-boundary=2 to both PE and non-PE builds, but to avoid breaking Winelib apps, we only want to use the flag on PE builds, and non-PE builds should continue to use force_align_arg_pointer instead?
MinGW should certainly be fixed to have a sane default stack alignment, but I agree with Zeb and Gabriel, there is no harm in explicitly requesting the correct stack alignment. Moreover, commit 62173699c38453777c7d5638ed2e779790506b75 caused several regressions, and it would be nice to fix them before releasing Wine 9.0.