[Starlingx-discuss] [Build] Removing Makefile for docker base image creation.

Hi all, Trying to fix this bug[0], I realize that the Makefile used to create the docker build base image can be removed in favor of the tb.sh script. I'm proposing this change[1] that will help to enable building in non- ubuntu systems. Also, I'm updating the documentation[2]. This change could break some workflows, please let me know if you have any objection. Best regards. -Erich [0] https://storyboard.openstack.org/#!/story/2002560 [1] https://review.openstack.org/#/c/637944/2 [2] https://review.openstack.org/#/c/637946/