Migrate toolchain and RPi kernel to current releases

[zehnm]

Migrate to the current kernel. The 4.19 kernel is planned to be an LTS kernel (long term support) afaik.
This ensures support of newer devices, e.g. using a Pi 4 for development which isn't supported with 4.14.

Main goals:

• Use current Buildroot LTS release 2020.02.x
• Update RPI kernel version to the defined 4.19.x version in the RPi Zero W Buildroot defconfig

Open issues:

• wpa_supplicant control socket is no longer created. Probably because of systemd configuration or the following change: buildroot/buildroot@c27708e
  --> works with provided wpa_supplicant.conf in /boot. Must be an initial configuration issue.
• Bluetooth serial console doesn't work anymore added in feat: Bluetooth console if marker file is present #56
  --> Bt pairing doesn't work anymore due to security changes, looks like we need a pairing agent now
• Update build toochain: releases built with Qt 5.12.4 don't run on the new Qt 5.12.8!
  • Test if app cross-compiled with Qt 5.12.8 runs on the current remote-os with Qt 5.12.4
    --> doesn't work, even though Qt promises backward & forward binary compatibility in patch releases 👎
  • Update GitHub actions with Qt 5.12.8

[zehnm]

Buildroot will be updated directly to 2020.02 once it's released and 2019.11 will be skipped.
Main reason for 2020.02 is the Qt update to version 5.12.7.

[zehnm]

Buildroot 2020.02 is released! It is a long term support release which will be supported with security and other important fixes until March 2021.
I will start a feature branch soon and test it.

[zehnm]

Created new branch for Buildroot 2020.02: Buildroot-2020.02.2

• Added workaround for node.js 12.6.x build error in 2020.02.2
  Existing bug: https://bugs.busybox.net/show_bug.cgi?id=12876

Edit: I will switch to Buildroot-2020.02.6 and remove the old branch. For documentation purposes, these are the patches required for compiling Node.js with 2020.02.2, which seems to be fixed now in .6:

0001-feat-Update-Buildroot-to-2020.02.2.patch.txt
0002-fix-Handle-Buildroot-bug-12876.patch.txt

[zehnm]

Current state:

• Remote app compiled with Qt 5.12.4 (as in all GitHub action releases for the current remote-os) doesn't run on Qt 5.12.8, which comes with Buildroot 2020.02.6

    WARN  default qrc:/main.qml:-1 File was compiled ahead of time with an incompatible version of Qt and the original file cannot be found. Please recompile
    /opt/yio/app/remote: relocation error: /opt/yio/app/remote: symbol 
    _ZN11QQmlPrivate13qmlunregisterENS_16RegistrationTypeEj version Qt_5 not defined in file libQt5Qml.so.5 with link time reference
  

  • Simply adding libQt5Qml.so.5.12.8 and replacing the libQt5Qml.so.5 symlink doesn't work: can't mix Qt version error
  • Remote app compiled on Qt 5.12.8 also doesn't run on Qt 5.12.4 👎
  • According to https://wiki.qt.io/Qt-Version-Compatibility this should not be an issue!

• Bluetooth pairing doesn't work anymore. On Linux, client now asks for a pin. MacOS just fails.

  • Looks like the new Bluez5 minor version update changed stuff in regards to security or uses other default settings.
  • My understanding is, that you need to have an agent now, which is responsible for pairing.
    The BlueZ examples are written in Python. That is not really an option for remote-os...
    There are lots and lots of pairing and headless pin / agent issues in the RPi forums & Stackoverflow!
  • Custom agent implementation in Qt: https://github.com/mdipirro/bluez-agent-qt
  • TODO test with /bin/bt-agent -c NoInputNoOutput -p /etc/bluetooth/pin.conf.
    Example: https://github.com/josefmtd/blue-agent/blob/master/blue-agent.service

• Initial WiFi setup doesn't work anymore: wpa_supplicant can't find wpa control socket.

  • However, a provided wpa_supplicant.conf file in /boot works.
  • There's an issue with the default wpa_supplicant configuration for the initial run, which prevents creating the wpa control socket.

[zehnm]

Open Issues:

• Initial WiFi setup doesn't work anymore: wpa_supplicant can't find wpa control socket.
  • fixed wpa_supplicant issues with a hard coded service file in /etc/systemd/system/wpa_supplicant.service
• Bluetooth pairing doesn't work anymore. On Linux, client now asks for a pin. MacOS just fails.
  • Bluetooth console is now working with bt-agent and NoInputNoOutput option
• Qt QML binary version incompatibility: 5.12.4 release doesn't run on 5.12.8
  • GitHub cross compile action need to build both versions
  • YIO update scripts need to check Qt version
  • Buildroot custom packages for YIO components should build YIO app & plugins from source, instead of downloading binary release from GitHub