// and recreate GOROOT.
	if err := adb("exec-out", "rm", "-rf", deviceRoot); err != nil {
		return err
	}

	// Build Go for Android.
	cmd = exec.Command(goTool, "install", "cmd")
	out, err = cmd.CombinedOutput()
	if err != nil {
		if len(bytes.TrimSpace(out)) > 0 {
			log.Printf("\n%s", out)
		}
		return fmt.Errorf("%v: %w", cmd, err)
	}
	if err := adb("exec-out", "mkdir", "-p", deviceGoroot); err != nil {

	}
	if missing > 0 {
		out += ".truncated"
	} else {
		out += ".complete"
	}
	fmt.Println(missing, "bytes missing. Truncating", len(filled)-lastValid-1, "from end.")
	mapped = mapped[:lastValid+1]
	err := os.WriteFile(out, mapped, os.ModePerm)
	if err != nil {
		return err
	}
	fmt.Println("Wrote output to", out)
	return nil