// for debugging the compiler, they are not settable using 'go env -w',
		// and so here we use os.Getenv, not cfg.Getenv.
		magic := []string{
			"GOCLOBBERDEADHASH",
			"GOSSAFUNC",
			"GOSSADIR",
			"GOCOMPILEDEBUG",
		}
		for _, env := range magic {
			if x := os.Getenv(env); x != "" {
				fmt.Fprintf(h, "magic %s=%s\n", env, x)
			}
		}

	case "gccgo":