Mark H Weaver said:
> I also asked on #parabola to find out how they deal with this issue.
> Apparently their IceCat is also old and unpatched, but they have
> scripts to modify Debian's Iceweasel to comply with the FSDG here:
>
>   https://projects.parabola.nu/abslibre.git/tree/libre/iceweasel
>
> We might consider adding this to Guix as well.

Also, Rubén's so-called "helper" script is available to the public. On
the GNUzilla Savannah project [0] hover over Source Code and select
either Use Git or Browse Sources Repository.

[0] http://savannah.gnu.org/projects/gnuzilla