SDK container: include circular dependency breaking packages in SDK

[t-lo]

This change builds all packages required to break circular dependencies in the "build SDK container" stage and includes these in the SDK image. This way, emerge- can be used right away and build_packages only builds packages with production USE flags.

The change significantly reduces the build time at the cost of a larger SDK image and longer SDK container build time. Uncompressed:

	Size before	Size after
all arches	7.75GB	9.29GB
arm64	5.7GB	6.58GB
amd64	5.64GB	6.45GB

How to use

• Clone the repo, check out this branch
• Fetch a recent SDK tarball to build the container image from, e.g. https://bincache.flatcar-linux.net/sdk/amd64/4098.0.0+nightly-20240919-2100/flatcar-sdk-amd64-4098.0.0+nightly-20240919-2100.tar.bz2
• Build an SDK container from the tarball, e.g. ./build_sdk_container_image -k flatcar-sdk-amd64-4098.0.0+nightly-20240919-2100.tar.bz2 (NOTE: this must run outside the SDK container, on your host)
• Emerge systemd in the new container image, which should fail if the circular dependencies were not included: ./run_sdk_container -t -C ghcr.io/flatcar/flatcar-sdk-amd64:4098.0.0-nightly-20240919-2100 emerge-amd64-usr systemd

Testing done

Ran the above, successfully emerged systemd for both amd64 and arm64.

Github actions

/update-sdk

[chewi]

Closed?

[github-actions]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/10964980395

[ader1990]

We have some issues sometimes with multiple kernel versions builds one after the other in the same environment, there is a btrfs loop that happens because of bpf (still no idea why, but some bad clean up / cache most likely). Let's see how it goes, I have not seen that issue in the last builds.