bug#19989: 25.0.50; Build instructions on Windows

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: martin rudalics <rudalics@gmx.at>,  19989@debbugs.gnu.org,  
> ilya@math.berkeley.edu
> Date: Fri, 06 Mar 2015 15:14:29 +0100
> 
> Another option is to recommend MSYS2 for those interested on building
> Emacs on Windows. It is a straightforward process.
> 
> I'll add the instructions one of this days.

Thanks!