Based on a suggestion by Andy Wingo at <https://lists.gnu.org/archive/html/guix-devel/2015-08/msg00753.html>. * gnu/build/svg.scm: New file. * gnu/local.mk (GNU_SYSTEM_MODULES): Add it. * gnu/system/grub.scm (svg->png): Add #:width and #:height. Rewrite to use (gnu build svg). (resize-image): Remove. (grub-background-image): Adjust accordingly.