Update rules to SR2020.4

This updates the rules to a local build of the rules repo
https://github.com/srobo/rules/ at revision
388d8a55c757cf0b9d5701abafbd92e989904d86.

This fixes a version number issue introduced in SR2020.3 and continues
to work RealOrangeOne/docker-pandoc#5.

Author: PeterJCLaw