Ticket 49475 - docker poc improvements.
Bug Description: Improve the docker poc to support intree builds.
Add a .mk file to help mak ethis easier for people to use.
Fix Description: Improve our specfile dependencies, our makefile
to use a with perl, and dockerfile to build from intree.
https://pagure.io/389-ds-base/issue/49475
Author: wibrown
Review by: mreynolds (Thanks!)