env do |env|
  env["build_root"] = env.build_root
  env["inc_h"] = "inc.h"

  env.Copy("copy_inc.h", "${inc_h}")
  env.depends("program.o", "${inc_h}")
  env.Object("program.o", "program.c")
  env.Program("program.exe", ["program.o", "inc.c"])

  inc_c = env.Command("inc.c",
                      [],
                      "CMD" => %w[ruby gen.rb ${_TARGET}],
                      "CMD_DESC" => "Generating")
  inc_c.produces("inc.h")
end