Hi Guix,

Doxygen uses a hardcoded "/bin/sh" to run "dot" (and maybe other 
processes as well) to generate documentation graphs, which fails in a 
build environment.  This patch adds the store item of bash-minimal as 
a prefix.

According to `guix refresh --list-dependent', this patch would cause 
689 packages to be rebuilt, so it probably shouldn't be applied on 
master.

best,

Thomas