Fix macOS Apple Silicon build

[ePirat]

Fixes the build of the plugin for macOS arm64 (Apple Silicon).

[juliansader]

Thanks for helping! I see that you made a few changes to travis.yml. Does this mean that you successfully built the ARM version on Travis instead of Appveyor?

[ePirat]

I did not look at Appveyor at all, I am not really familiar and had no idea it could be used for macOS builds. I've only changed the travis command because it was the only place I found where a build command was found. If you want I can help set up proper macOS builds for x86_64, ARM, Universal using either Travis or GitHub Actions as those two I am quite familiar with and could do it easily.

Ideally the project would have a proper build system instead of just some compiler command somewhere, to help with portability and easily adapting things for different architectures.

[gnai]

Does this mean it should work flawlessly on the M1 machines ?
Thank you :)