bug#19989: 25.0.50; Build instructions on Windows

[Eli Zaretskii]

> Date: Fri, 06 Mar 2015 10:21:49 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: 19989@debbugs.gnu.org
> 
> Maybe I'm wrong but it appears that every DL and installation step has
> to be prepared carefully wrt overwriting (or not) previously installed
> libraries.

The only rule I follow (religiously, btw) is not to overwrite a DLL
with an older one, judging by its time stamp.  I didn't find any other
issues.

> Using mingw-get (which I did) is complicated as well if you want to
> avoid falling into one of the traps mentioned in this thread.

The question is: can we amend the instructions to make them less
error-prone?  The manual instructions are very detailed, and I can
vouch for their correctness because that's what I used.  The mingw-get
instructions are from someone else, so those who use it are kindly
requested to help with making them better, as much as possible.