%desktop-services now depends on Qt 5, via colord

[Mark H Weaver <mhw@netris.org>]

Hi Tobias,

me@tobias.gr (Tobias Geerinckx-Rice) writes:

> nckx pushed a commit to branch master
> in repository guix.
>
> commit 407ef4b38ad394e0b63320b029d95afdd3da6888
> Author: Tobias Geerinckx-Rice <me@tobias.gr>
> Date:   Tue Jun 19 20:02:42 2018 +0200
>
>     gnu: hplip: Add Qt GUI support.
>     
>     Some tools (like ‘hp-toolbox’) still refuse to launch, but at least
>     others (like ‘hp-systrax’) now seem to work.
>     
>     * gnu/packages/cups.scm (hplip)[arguments]: Add #configure-flags for Qt.
>     [inputs]: Add python-gobject and python-pyqt.

Until this commit, it was possible to build a desktop system without Qt.
No longer.

This commit effectively added most of Qt 5 as a new dependency of
'colord' (via 'sane-backends' and 'hplip'), which in turn means that
_any_ GuixSD system that uses %desktop-services now depends on Qt 5
libraries, including:

   qtbase
   qtconnectivity
   qtdeclarative
   qtlocation
   qtmultimedia
   qtsensors
   qtserialport
   qtsvg
   qttools
   qtwebchannel
   qtwebsockets
   qtx11extras
   qtxmlpatterns

I would greatly prefer to preserve a straightforward way to build a
desktop system, e.g. a GNOME system, without building Qt 5.

Thoughts?

       Mark