// a fatal error upon reaching maxSwitch.
	// That should be enough to see the repetition.
	maxSwitch = 100
)

// FilterEnv returns a copy of env with internal GOTOOLCHAIN environment
// variables filtered out.
func FilterEnv(env []string) []string {
	// Note: Don't need to filter out targetEnv because Switch does that.
	var out []string
	for _, e := range env {

	// In theory all the commands we invoke should have
	// the same default computation of these as we do,
	// but in practice there might be skew
	// This makes sure we all agree.
	cfg.OrigEnv = toolchain.FilterEnv(os.Environ())
	cfg.CmdEnv = envcmd.MkEnv()
	for _, env := range cfg.CmdEnv {
		if os.Getenv(env.Name) != env.Value {
			os.Setenv(env.Name, env.Value)
		}
	}

	cmd.Flag.Usage = func() { cmd.Usage() }