Enable CONFIG_IKCONFIG_PROC on arm64 kernel

[liulanze]

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

Enable CONFIG_IKCONFIG_PROC=y on arm64 for parity with x86_64, exposing the kernel build config at /proc/config.gz at runtime. This is required by kubeadm and other tools that need to read kernel config. The option was already enabled on x86_64 but missing on arm64.

Does this affect the toolchain?

NO

Test Methodology

• Pipeline build id: https://dev.azure.com/mariner-org/mariner/_build/results?buildId=1091388&view=results

[liulanze]

The buddy build passed the Build and Test step successfully. The License Check step failed with pre-existing warnings about %doc files in kernel-docs/kernel-tools RPMs being flagged as potential license files (bpf_licensing.rst, COPYING-logo, license-rules.rst, LICENSE.FlashPoint). These warnings exist in the base kernel spec and are unrelated to this config change, that they would appear on any kernel buddy build.

The PR check pipelines show failures in systemd and libguestfs package tests, but these are pre-existing and unrelated to our change, the buddy build's kernel build step passed successfully.

systemd tests fail due to container/sandbox limitations (missing libvirtd, missing systemd-detect-virt, broken RPM macros), and the failures are identical on both AMD64 and ARM64. Our change only touches kernel config files.