[zizmor] Security fixes for workflow vulnerabilities

[Vombato]

🔒 Security Fixes

This PR resolves security vulnerabilities detected by Zizmor.

Issue Resolved

• Closes vechain/security#328

Summary

• ✅ Applied 0 automatic security fixes
• 📝 Modified 1 workflow file(s)

Files Changed

• .github/workflows/build.yml

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Review Checklist

• [ ] Review all changes
• [ ] Verify workflows still work
• [ ] Merge when ready