Use current LTS buildroot release 2021.02.8, drop busybox patch that is
no longer needed.

Stop building ppc64 which is failing boot-test with "kernel too old".

Change-Id: I19603cc50a11153dcf9ee30958754737782b5e14

This has multiple advantages about the previous setup:

- Set up all available interfaces automatically
- Handle IPv6 variants properly (SLAAC vs. DHCPv6)

Add some further networking tools for easier debugging

Change-Id: Idf04a48c04127b2a40fdaea47e7eea39383b1125

Use the latest grub and linux kernel versions from Ubuntu 22.04 LTS.
Update the README accordingly.

Build images on Ubuntu 22.04, too. Switch from python 2 to 3.
Stop building i386 for which no recent kernels are available.

Change-Id: I0e58449cd4bd3d526efd5b99b1f84fabda5c5813

Ubuntu 22.04 packages use zstd compression method. It is not
supported in upstream dpkg so build was possible only on
Ubuntu 22.04 release.

Change-Id: I9856e4072462d8a1e280768bb71c1790837c6005

Configs need to be updated

Change-Id: I7573775d6375e5f8c3deb84c8cc5d6e3416de536

- arm moved to armv7/cortex-a8
- bind disabled (have to check)
- tcpdump, traceroute, dhcpcd enabled

arm, aarch64, x86_64 build and boot fine
ppc64le needs work

Change-Id: I3f96ac790fe66fe903ee007aa116c012266c6f2f

Ubuntu 22.04 does not support them so we do not too:

- i386    (32-bit x86)
- powerpc (32-bit)
- ppc64   (64-bit big endian)

Also dropped support for older kernel releases which was used for
powerpc/ppc64.

Change-Id: Idc41fe181034c2b6d9e45bac7ac114174da3a789

Instead of creating those directories in parent directory and then
symlinking them back.

This way there is no need to scroll whole build log just to see did it
booted properly.

Looks like they block traffic coming from github.