bug#36828: 27.0.50; Uninstalled emacs shows installed documentation

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Date: Sun, 28 Jul 2019 17:07:20 +0200
> 
> src/emacs -Q
> 
> C-h N
> 
> M-: (buffer-file-name)
> 
> "/usr/local/share/emacs/27.0.50/etc/NEWS"
> 
> Maybe this is caused because, time ago, I installed Emacs from the build
> directory, but since I pulled new changes and rebuilt Emacs. So now
> emacs instances launched from the build directory are showing stalled
> documentation.

Emacs tries the installation directory first, and only falls back to
the build directory if the installation directory doesn't exist.