fix(variant): Arduino Nano ESP32 variant fix for core 3

[JAndrassy]

I don't know what hack that is including cpp files, but without this PR every build for this board fails with core 3. linker can't find bytes2hex from HEXBuilder.

I just unpacked my new Nano ESP32. I wonder why nobody cares about this board with core 3.

[github-actions]

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👋 Hello JAndrassy, we appreciate your contribution to this project!

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[me-no-dev]

@pillo79 PTAL

[github-actions]

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[pillo79]

Sorry, my bad for not checking it after the betas. I confirm this is the proper fix, thanks @JAndrassy! 🙇