chore: Image builder demo updates

[aknot242]

Proposed changes

• Switch to JSON args to resolve docker build warnings
• Explicitly set arch for NAP WAF builds for when building from ARM systems

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[github-actions]

✅ All required contributors have signed the F5 CLA for this PR. Thank you!
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[aknot242]

I have hereby read the F5 CLA and agree to its terms