class RbSys::CargoBuilder

def write_deffile(dest_path)
  dest_dir = File.dirname(final_extension_path(dest_path))
  FileUtils.mkdir_p(dest_dir)
  deffile_path = File.join(dest_dir, "#{spec.name}-#{RbConfig::CONFIG["arch"]}.def")
  export_prefix = makefile_config("EXPORT_PREFIX") || ""
  File.open(deffile_path, "w") do |f|
    f.puts "EXPORTS"
    f.puts "#{export_prefix.strip}Init_#{spec.name}"
  end
  deffile_path
end