code: function build(mode, system, cdef, out, cb) {
      logger.info('building');
      out.stdout('--> building');
  
      builder.build(mode, system, cdef, out, function(err, specific) {
        if (err) { logger.error(err); return cb(err); }
        cb(err);
      });
    }
docs: build the container
  system - the system definition
  cdef - contianer definition block
  out - ouput stream
  cb - complete callback