tools: add a manifest reconciliation tool to refresh the manifest after hook changes

[Meulengracht]

Snapcraft uses the chisel manifest to detect packages installed, and due to the hooks trimming packages, including the python hiding, the manifest unfortunately defines packages/libraries that are simply not available. This breaks snap builds against core26.

Overall the script does two things;

• Automatically prunes entries that do not have a physical file present
• Introduces a --exclude-python which prunes python entries as we are effectively hiding python. When we reach core28 we can remove this again, thus the reason as to why it's a separate switch
• Refreshes the manifest header with an updated count

SNAPDENG-36930

[Copilot]

Pull request overview

This PR introduces a post-hook reconciliation step to ensure Chisel’s manifest.wall matches the final rootfs contents after hooks remove files (notably around hidden Python), preventing Snapcraft from seeing packages/libraries that are no longer present.

Changes:

• Add tools/refresh-manifest.py to prune stale manifest.wall entries based on actual rootfs contents, with an option to exclude Python-related entries.
• Invoke the reconciliation tool from the hooks Makefile target after hook execution.
• Add zstd as a build dependency (currently in the chisel-libs part).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tools/refresh-manifest.py	New reconciliation tool that filters manifest.wall based on rootfs existence and optional Python exclusion.
Makefile	Runs the reconciliation tool after hooks to keep the manifest aligned with the shipped rootfs.
snapcraft.yaml	Adds zstd build dependency (needed for zstdcat/zstd used by the reconciliation tool).

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.