[fasttrack 3.0] kernel-64k: Enable signature verification of kexec kernel

[rlmenge]

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 (./LICENSES-AND-NOTICES/SPECS/data/licenses.json, ./LICENSES-AND-NOTICES/SPECS/LICENSES-MAP.md, ./LICENSES-AND-NOTICES/SPECS/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

While the key for the kernel-64k was updated to match the updated key brought into #10961

The kexec changes did not transfer over. This results in kexec using IMA to verify the kernel signature instead of the desired kexec signature verification path which is able to use the kernel's built-in keys

Change Log

• Copy the kexec sig changes from d647152 onto the kernel-64k

Does this affect the toolchain?

YES

Associated issues

• 576787640

Test Methodology

• Pipeline build id:

[rlmenge]

close in favor of #11569