Tar build artifacts

This action creates a tarball with kbuild-output and other build artifacts necessary to run the selftests.

The action is expected to be executed by a workflow with access to the Linux kernel repository.

Required inputs

• arch - Kernel build architecture, required to find image_name
• archive - path to the produced .zst archive
• kbuild-output - Path to the kernel build output
• repo-root - Path to the root of the Linux kernel repository

Archive options

Essential content of the directory passed via kbuild-output input is always included in the tarball.

For selftests artifacts the script checks environment variables to determine what to include. These are handled as bash flags: emptystring means false, any other value means true.

• ARCHIVE_BPF_SELFTESTS - add tools/testing/selftests/bpf binaries under selftests/bpf in the tarball
• ARCHIVE_MAKE_HELPERS - add all the Linux repo makefiles and other scripts
• ARCHIVE_SCHED_EXT_SELFTESTS - add tools/testing/selftests/sched_ext binaries under selftests/sched_ext in the tarball