bug#19989: 25.0.50; Build instructions on Windows

[martin rudalics]

>> The problem is that most users are trying to be clever.  At least I did
>> and AFAICT Ilya did too.
>
> Yes — the first 8 times.  The last try was by following the
> instructions literally (as close as I can after 9 hours of
> unsuccessful trying).
>
>>   That's of no help.  What's really needed is a
>> stubborn, dense person who complains immediately when something doesn't
>> work out as written in INSTALL.
>
> This is exactly what I do.

You didn't.  Otherwise, you would have started right away "by following
the instructions literally".  And an important guideline is: Never do
anything extraneous when following INSTALL instructions.  Unfortunately,
installers likes those for mingw/msys offer too many pitfalls in this
area.  Especially when resolving dependencies.

martin