Mingw(32) is rather poorly maintaned and has quite a lot of bugs. And
because our Windows cross builds were also poorly maintained and most of
the cross-tests were broken as well, I'm just taking this step and try
to switch to mingw-w64 for everything "cross Windows".
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
The winpthreads library is part of the same source package, so let's
just override the name and the source directory.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>