bug#19811: Attempt to graft texlive times out after one hour

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

On my i686 Libreboot X60, two consecutive attempts to run "guix package
-u" have failed with the following message:

--8<---------------cut here---------------start------------->8---
grafting '/gnu/store/i8iiv9qd1jndwxxr2h563fwwn0997xkx-cups-2.0.1' -> '/gnu/store/nrdr51fkncjm5nqkx70576g25l4ka5na-cups-2.0.1'...
grafting '/gnu/store/y2f71ym41fp803ysf62k1ajk687xd684-xsensors-0.70' -> '/gnu/store/vhjp122fax73k4vags86q6gqzk5qj232-xsensors-0.70'...
building of `/gnu/store/an8an36igcaasvg72kcjph7ns7ssgy6d-texlive-2014.drv' timed out after 3600 seconds of silence
cannot build derivation `/gnu/store/c2fab7ppy5xqgsglvkdp489n95278izx-profile.drv': 1 dependencies couldn't be built
guix package: error: build failed: build of `/gnu/store/c2fab7ppy5xqgsglvkdp489n95278izx-profile.drv' failed
--8<---------------cut here---------------end--------------->8---

I guess that my machine and rotating disk are too slow to graft texlive
within an hour.

Apart from that, there are a few specific problems:

* It never notified me that it was grafting texlive.  Are those messages
  not printed until after the grafts have completed?

* I later discovered the --timeout option for 'guix build' (also
  supported by 'guix package') but the manual claims that "By default
  there is no timeout".  This seems to be incorrect.

     Mark