Elixir requires that we use version of the form `Major.Minor.Patch`.
Also, Mix requires dependecies to be declared in `rebar.config` so it
can include the header files correctly.
Surprisingly enough, by doing small cirurgical changes in the existing
EMQX control scripts, we are able to get it running with Elixir and
with existing functionalities (`console`, `remote_console`, `start`,
`stop`, `ctl`, `foreground`, `eval`).
This commit enables a minimal working build of EMQX release using
Mix. However, to properly start the release, several configuration
steps are still missing. A `mix_release.sh` script does a few hacks
to get the release built with Mix to start properly, by first assuming
that `make emqx` has been run prior to the release, ran once to
generate the `app.*.config` files, and then it copies that and some
other files to the expected places.
Also, `emqx_telemetry` hangs the start procedure because it thinks
it's in an official release and tries to make a request. We disable
it temporarily via config just to get a working build for now.
Thales Macedo Garitezi