func compilerEnv(envName, def string) map[string]string {
	m := map[string]string{"": def}

	if env := os.Getenv(envName); env != "" {
		m[""] = env
	}
	if env := os.Getenv(envName + "_FOR_TARGET"); env != "" {
		if gohostos != goos || gohostarch != goarch {
			m[gohostos+"/"+gohostarch] = m[""]
		}
		m[""] = env
	}

	for _, goos := range okgoos {
		for _, goarch := range okgoarch {