Chrome OS Flex

1. cros_debug: enable debug
2. address crostini install issue for some old Intel CPU: kvm-intel.vmentry_l1d_flush=always

1. crostini-multi-container
2. crosh-swa
3. #allow-scroll-settings
4. #enable-libinput-to-handle-touchpad

from: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_mode.md#disable-verity

  sudo /usr/share/vboot/bin/make_dev_ssd.sh --force --remove_rootfs_verification
  # after reboot
  sudo mount -o rw,remount /

  sudo /usr/libexec/debugd/helpers/dev_features_ssh