Build raspberrypi4 image from Yocto Project

raspberrypi4_notes.txt

* Yocto Project Quick Build
  https://www.yoctoproject.org/docs/2.7.1/brief-yoctoprojectqs/brief-yoctoprojectqs.html
* meta-raspberrypi
  http://git.yoctoproject.org/cgit.cgi/meta-raspberrypi/about/?h=warrior
* Building Raspberry Pi Systems with Yocto
  https://jumpnowtek.com/rpi/Raspberry-Pi-Systems-with-Yocto.html
* coldnew.github.io:
  https://coldnew.github.io/c3e8558e/
  https://coldnew.github.io/64f655a5/
* Useful bitbake commands
  https://community.nxp.com/docs/DOC-94953
* OpenEmbedded Layer Index
  https://layers.openembedded.org/layerindex/branch/master/layers/

[Build Host Packages]
On Ubuntu 18.04.3 LTS:
sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib \
     build-essential chrpath socat cpio python python3 python3-pip python3-pexpect \
     xz-utils debianutils iputils-ping python3-git python3-jinja2 libegl1-mesa libsdl1.2-dev \
     xterm

[Use Git to Clone Poky]
git clone git://git.yoctoproject.org/poky
cd poky
git checkout tags/yocto-2.7.1 -b my-yocto-2.7.1

[Clone meta-raspberrypi and its dependencies]
git clone -b warrior git://git.openembedded.org/meta-openembedded
git clone -b warrior git://git.yoctoproject.org/meta-raspberrypi

[Building Your Image]
source oe-init-build-env
(will create 'build/conf' dir and cd to it)

(check build/conf/bblayers.conf)
bitbake-layers add-layer ../meta-openembedded/meta-oe
bitbake-layers add-layer ../meta-raspberrypi

(modify build/conf/local.conf)
MACHINE ?= "raspberrypi4"

bitbake core-image-base