bug#36828: 27.0.50; Uninstalled emacs shows installed documentation

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: stepnem@gmail.com,  36828@debbugs.gnu.org
> Date: Mon, 28 Oct 2019 20:40:03 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> Once we know that we are running a non-installed emacs, detecting that
> >> it is an out-of-source build seems quite easy, because the build
> >> directory contains build artifacts without the sources.
> >
> > Yes.  But how to detect that we are running non-installed?
> 
> Checking for the presence of the "Makefile" file using the same method
> we use for "NEWS".

Presence where?

Anyway, Makefile is too common a file, I think we should look for
something more specific to Emacs.