Currently the source_path_option overrides any source-paths in air-config.xml. Instead, it should use the append +=
operator when specifying the local source-paths, like so:

module Airake::Project

  def source_path_option
    @source_paths ||= lib_source_paths
    @source_paths.empty? ? "" : @source_paths.map { |path| "-source-path+='#{path}'" }.join(' ')
  end
  
end