Hello Guix,

The attached patch eliminates the use of 'inkscape' and 'imagemagick' to
convert our grub background image from SVG to PNG.  The job is now done
using 'librsvg' [1] via Guile's dynamic FFI.  I was unable to perform
the needed scaling using the 'rsvg-convert' program, so I had to use
librsvg directly.

As a side benefit, the resulting image quality should be superior when
scaling is performed, because scaling is now effectively done in the
vector representation during rendering, whereas previously it was done
in the raster representation as a separate step.

What do you think?

      Mark


[1] Note that in the past, 'librsvg' was unable to properly convert our
    SVG file, but that problem seems to be fixed.