gdk reconfigure improvements

What does this Merge Request do?

This MR creates the reconfigure: make target so if desired one can run make reconfigure as well as printing to the console when a reconfigure has successfully completed.

While a longer term goal is to ideally make the Makefile obsolete, I feel there is benefit here moving the specifics of what a reconfigure actually does into the Makefile to make it easier in the future to swap out.

$ make reconfigure

------------------------------------------------------------
Installing gitlab-org/gitlab Ruby gems
------------------------------------------------------------
Bundle complete! 254 Gemfile dependencies, 485 gems now installed.
Gems in the group production were not installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

--snip--

> Reconfigured as of 2020-06-04 14:59:29

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.