func envOr(key, def string) string {
	val := Getenv(key)
	if val == "" {
		val = def
	}
	return val
}

// There is a copy of findGOROOT, isSameDir, and isGOROOT in
// x/tools/cmd/godoc/goroot.go.
// Try to keep them in sync for now.

// findGOROOT returns the GOROOT value, using either an explicitly
// provided environment variable, a GOROOT that contains the current

		return err
	}
	s, err := io.ReadAll(stat)
	if err != nil {
		return err
	}
	if string(s) == goVersion {
		return nil
	}

	goroot, err := findGoroot()
	if err != nil {
		return err
	}

	// Delete the device's GOROOT, GOPATH and any leftover test data,
	// and recreate GOROOT.
	if err := adb("exec-out", "rm", "-rf", deviceRoot); err != nil {

	for _, envVar := range strings.Fields(cfg.KnownEnv) {
		os.Getenv(envVar)
	}
	return path
}

var (
	gorootOnce sync.Once
	gorootPath string
	gorootErr  error
)

func findGOROOT() (string, error) {
	gorootOnce.Do(func() {
		gorootPath = runtime.GOROOT()
		if gorootPath != "" {
			// If runtime.GOROOT() is non-empty, assume that it is valid.
			//