Enable (more) Azure extensions to work on Flatcar

[jepio]

Current situation

Currently Azure extensions do not work on Flatcar because:

• Flatcar does not ship the required dependencies
• the extensions explicitly list supported distributions, and these lists dont include flatcar for various reasons

What we tried

flatcar-archive/coreos-overlay#1815
By adding a full python interpreter, with all standard modules, to the OEM partition we got the VMBackup extension to work. This work is not mergeable as is, because it consumes third party binaries. We initially only tested this on arm64, but we should get an amd64 dev build with this change out so that we can test how many other extensions this enables.

Next steps

These are rough points, in no particular order, and a only a subset may be needed to accomplish the goal:

• rebuild a current amd64 Flatcar release including [RFC] dev-lang/python-oem: use python from python-build-standalone project flatcar-archive/coreos-overlay#1815 to unblock further extension testing
• figure out how to rebuild the python-build-standalone binaries and include into our build process
• productize OEM sysexts for Azure. This still requires figuring out what is inside the sysext:
  • is it the output of python-build-standalone
  • is it some other dependency-less python installation
  • is it a standard python install based on our ebuild, but the OEM file gets auto-updated with every release?

Extensions we've looked at

• VMBackup

[pothos]

Have started a rebuild of the latest Alpha: http://192.168.42.7:8080/job/os/job/manifest/5823/cldsv/ with
0001-dev-lang-python-oem-use-python-from-python-build-sta.patch

[pothos]

The systemd-sysext Azure OEM image now provides a full python. Since the dependencies of Azure extensions are in flux we would have to catch up with additional Python libs to install every now and then. The better approach would be if the extensions become self-contained by bundling their dependencies.

Can we close this issue or is there a particular extensions that we could easily unblock (at least for some time)?