if err != nil {
		return nil, err
	}
	env := []string{
		pathEnvName() + "=" + testBin + string(filepath.ListSeparator) + os.Getenv(pathEnvName()),
		homeEnvName() + "=/no-home",
		"CCACHE_DISABLE=1", // ccache breaks with non-existent HOME
		"GOARCH=" + runtime.GOARCH,
		"TESTGO_GOHOSTARCH=" + goHostArch,
		"GOCACHE=" + testGOCACHE,
		"GOCOVERDIR=" + os.Getenv("GOCOVERDIR"),

	// On some systems the default C compiler is ccache.
	// Setting HOME to a non-existent directory will break
	// those systems. Disable ccache and use real compiler. Issue 17668.
	os.Setenv("CCACHE_DISABLE", "1")
	if cfg.Getenv("GOCACHE") == "" {
		os.Setenv("GOCACHE", testGOCACHE) // because $HOME is gone
	}

	if testenv.Builder() != "" || os.Getenv("GIT_TRACE_CURL") == "1" {