Subject: [bug#34832] Go build system updates

From: Leo Famulari <[email-masked]>
Date: Wed, 13 Mar 2019 18:21:15 -0400

This is currently being built on berlin.guixsd.org:

https://berlin.guixsd.org/jobset/wip-go-build-system

I will push these changes to the master branch as soon as they are
ready on Berlin.