Switch to building the only moreutils utility we actually need (sponge). This results in having less unused stuff in the Guix environment (i.e all the other moreutils utilities), and, the dependency graph is simplified. i.e we no-longer have a dependency on perl, docbook etc, for this package.
Current moreutils dependency graph:
In the Guix env, chronic, combine, errno, ifdata, ifne, isutf8, lckdo, mispipe, parallel, pee, ts, vidir, vipe & zrun (plus their *.real variants) are removed.
