Add cleanup script to base images

[romoh]

Remove /srv linking that is created by the toolchain & filesystems package. Toolkit and filesystem package unnecessarily symlink /var/srv & /srv which interferes with other scenarios. This will be fixed in Mariner 3.0, this PR is a mitigation for 2.0 images.

More details:

ln -svfn var/srv %{buildroot}/srv
srv symlink created by the toolkit https://github.com/microsoft/CBL-Mariner/blob/4e4223205fdd0154713821430f2224290ff94a74/toolkit/scripts/toolchain/container/toolchain_initial_chroot_setup.sh#L41
The symlink is also created by https://github.com/microsoft/CBL-Mariner/blob/4e4223205fdd0154713821430f2224290ff94a74/SPECS/filesystem/filesystem.spec#L63

On any mariner image, the symlink is left behind which is interfering with scenarios where customers want to mount a volume over /srv

PR also adds cleanup for any logs that may be left after the build process is completed.

Merge Checklist

All boxes should be checked before merging the PR (just tick any boxes which don't apply to this PR)

• The toolchain has been rebuilt successfully (or no changes were made to it)
• The toolchain/worker package manifests are up-to-date
• Any updated packages successfully build (or no packages were changed)
• Packages depending on static components modified in this PR (Golang, *-static subpackages, etc.) have had their Release tag incremented.
• Package tests (%check section) have been verified with RUN_CHECK=y for existing SPEC files, or added to new SPEC files
• All package sources are available
• cgmanifest files are up-to-date and sorted (./cgmanifest.json, ./toolkit/scripts/toolchain/cgmanifest.json, .github/workflows/cgmanifest.json)
• LICENSE-MAP files are up-to-date (./SPECS/LICENSES-AND-NOTICES/data/licenses.json, ./SPECS/LICENSES-AND-NOTICES/LICENSES-MAP.md, ./SPECS/LICENSES-AND-NOTICES/LICENSE-EXCEPTIONS.PHOTON)
• All source files have up-to-date hashes in the *.signatures.json files
• sudo make go-tidy-all and sudo make go-test-coverage pass
• Documentation has been updated to match any changes to the build system
• Ready to merge

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Summary

What does the PR accomplish, why was it needed?

Does this affect the toolchain?

NO

Test Methodology

Built locally and validated.

just comment

[cwize1]

The '/srv' -> '/var/srv' symlink is created by the filesystem package, not the toolchain.

[romoh]

The '/srv' -> '/var/srv' symlink is created by the filesystem package, not the toolchain.

It is created by both.