Add relx configuration for Riak.

[cmeiklejohn]

Add a configuration for relx that uses the rebar3 cuttlefish plugin for properly building the configurations required schema files.

Cuttlefish compilation is still preventing the node from starting because cuttlefish doesn't run escript using the application libraries. Therefore, any schema file that references a library in lib -- for instance, the Riak KV files reference a function in riak_core_throttle that is unavailable for cuttlefish unless the application libraries are loaded.

Another issue here is that in the configuration that uses a cd dirname $0 && /bin/pwd to derive the release path. This is a problem because relx uses the escape functionality of mustache to conver this && to & -- this is not a valid unix command. Since there is no known way to prevent this escaping of a literal, this has been replaced by a ; under the assumption that the directory change to dirname $0 command will not fail.

Before this can be merged, the following issue has to be addressed:
vernemq/rebar3_cuttlefish#35

cc: @martincox @martinsumner

[llelf]

Another issue here is that in the configuration that uses a cd dirname $0 && /bin/pwd to derive the release path. This is a problem because relx uses the escape functionality of mustache to conver this && to & -- this is not a valid unix command.

if cd "`dirname "$E"`"; then pwd; fi

?

[cmeiklejohn]

It would need an else branch, and I'm not sure what's safe to use there?

[llelf]

It doesn't need else, it is practically the same as &&.

[ThomasArts]

This is outdated. We now have a release build in place.