feat: add sysext build scripts #2

	name: Build and release Systemd sysext images
	on:
	push:
	tags:
	- '*'

	env:
	RUNC_VERSION: v1.2.0-rc.2
	CONTAINERD_VERSION: 2.0.0-rc.3

	jobs:
	build:
	runs-on: ubuntu-22.04
	permissions:
	# allow the action to create a release
	contents: write
	steps:
	# checkout the sources
	- uses: actions/checkout@v4

	# prepare build host
	- name: install prerequisites
	run: \|
	set -euxo pipefail

	sudo apt update -qq && sudo apt install -yqq \
	curl \
	jq \
	squashfs-tools \
	xz-utils \
	gawk

	- name: build release artifacts
	run: \|
	TAG=${{ github.ref_name }} ./create_containerd_sysext.sh $CONTAINERD_VERSION containerd-nine

	- name: create a new latest release with all artifacts
	uses: softprops/action-gh-release@v1
	with:
	files: \|
	SHA256SUMS
	*.raw
	*.conf

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