[PATCH] Fix cache dir resolving on Windows

[Eli Zaretskii]

> Cc: gdb-patches@sourceware.org
> From: Simon Marchi <simark@simark.ca>
> Date: Tue, 4 Jun 2019 11:05:52 -0400
> 
> >   https://docs.microsoft.com/en-us/windows/desktop/shell/knownfolderid
> >   https://docs.microsoft.com/en-us/windows/desktop/shell/csidl
> > 
> > But maybe we don't care about that.  I know that many applications
> > ported from Unix don't.
> 
> If it's not too complicated to do The Right Thing (use these  and be a good citizen,
> I would prefer that.  But I won't be the one writing the change for Windows
> and maintaining it, so I won't force it either.

If we want to follow the recommendations, it's just the matter of
using a different environment variable: APPDATA instead of
USERPROFILE.  It is usually a subdirectory of USERPROFILE.