macOS: Investigate if we can turn on the hardened runtime

[erikjv]

The hardened runtime protects against certain (local) attacks.

We have to check if we can enable it, because QtDeclarative runs with a JIT (by default).

Apple documentation: https://developer.apple.com/documentation/security/hardened-runtime

Also: XCODE_ATTRIBUTE_ENABLE_HARDENED_RUNTIME

[github-actions]

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