[HarfBuzz] Patches for building HarfBuzz with mingw.org's MinGW

[Eli Zaretskii]

> From: Behdad Esfahbod <behdad at behdad.org>
> Date: Tue, 4 Jun 2019 13:08:35 -0700
> Cc: "harfbuzz at lists.freedesktop.org" <harfbuzz at lists.freedesktop.org>
> 
> I can't say I'm super-excited about adding more workarounds, specially since I don't even understand why you
> can't use mingw64 instead.
> 
> At any rate, I'm not one to judge.  Please open a github Pull Request with your changes and we'll go from
> there.

Done, I think.