gcc currently assumes the stack alignment for i686-w64-mingw32 is 16, which is
essentially wrong. It works around this in most cases by applying -mstackrealign
when SSE is in use. However, this doesn't address the case of manually aligned
types (i.e. DECLSPEC_ALIGN), and it also for some reason doesn't seem to apply
when -mavx512f is in use, which seems to be an independent gcc bug.

The correct solution on the gcc end is not to assume that the stack is 4-byte
aligned. -mpreferred-stack-boundary=2 achieves exactly this, and there is motion
upstream to address this by effectively making this setting the default. Since
this will take time to propagate downstream, though, it seems prudent to address
this bug locally by essentially applying the same fix downstream.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55007
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55899