Build the release inside a Docker container for cross-compilation.

The Docker image can be configured via builder.docker in config/xamal.exs:

• docker: true uses a default hexpm/elixir image
• docker: "image:tag" uses the specified image

Builder args from builder.args are passed as environment variables via -e flags.

Build the release locally with mix release.

Create a tarball from the built release.

Upload the tarball to a remote host and unpack it.

SCP command to upload tarball to a host.

The tarball filename.

The local tarball path.

Unpack the tarball on the remote host.

Upload the env file for a role to the remote host.