ci: run linux64_nowallet jobs on ARM runners

[thepastaclaw]

Summary

Move the linux64_nowallet depends, build, and test jobs to ARM runners, matching the pattern already used by linux64_multiprocess and linux64_tsan.

Changes

In build.yml, switch runs-on for three jobs from RUNNER_AMD64 to RUNNER_ARM64:

• depends-linux64_nowallet
• src-linux64_nowallet
• test-linux64_nowallet

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[thepastaclaw]

Review Gate

Commit: 35dfbf93

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[github-actions]

This pull request has conflicts, please rebase.

[thepastaclaw]

Closing as superseded by #7232.

The broader ARM-runner migration in #7232 explicitly keeps linux64_nowallet on x86 as the remaining native x86_64 coverage lane, so this narrower change no longer matches the intended CI layout.

No branch refresh/rebase is needed here: the current head is already cleanly mergeable, but the design direction moved on.