fix(deps): add missing cargo-zigbuild dependency for macOS cross-compilation

[benoitf]

Summary

Add the missing cargo-zigbuild dependency to mise.toml so that macOS cross-compilation works out of the box. Without this, it fails on mise run vm:rootfs --base step

Related Issue

#917

Changes

• Add cargo:cargo-zigbuild v0.22.3 to mise.toml, scoped to macOS only (os = ["macos"])

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (if applicable)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

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