"-i", appdir,
		))
		if out, err := cmd.CombinedOutput(); err != nil {
			// Sometimes, installing the app fails for some reason.
			// Give the device a few seconds and try again.
			if attempt < 5 {
				time.Sleep(5 * time.Second)
				attempt++
				continue
			}
			os.Stderr.Write(out)
			return fmt.Errorf("ideviceinstaller -i %q: %v (%d attempts)", appdir, err, attempt)
		}
		return nil
	}
}

	// it to be ready. adb wait-for-device is not enough, we have to
	// wait for sys.boot_completed.
	if err := adb("wait-for-device", "exec-out", "while [[ -z $(getprop sys.boot_completed) ]]; do sleep 1; done;"); err != nil {
		return 0, err
	}

	// Done once per make.bash.
	if err := adbCopyGoroot(); err != nil {
		return 0, err
	}