Support macOS apple silicon

[TotemaT]

Hello !

First of all, thanks for the project; it's exactly what I needed for a project :)

I tweaked your scripts to allow building for macOS with arm64/apple silicon chips.

I then built it locally using the commands I found in your github workflow and tested it by running the example provided. (I also changed the URL for the pre-built binaries in setup.dart to fetch from my localhost while I was testing 👍)

Tested on a MacBook pro with an Apple M1 Pro running macOS Sonoma 14.3.1

Hope that can be merged/released soon, keep me updated if you need more info for this pull request or if you want me to test more stuff on macOS 👍

[rainyl]

Great! Thanks for your PR, I will test it as soon as possible.
BTW, I am not familiar with Apple development, so I want to know whether it is possible to build a arm64 library on x64 macos?

[TotemaT]

I don't know, but I guess it should be possible.

On the other hand, I can tell you that building (and running, through Rosetta) a x64 library on an Apple silicon device is possible - which is good since intel/x64 macs have been (or are being) discontinued by Apple

[rainyl]

Finally, I didn't managed to compile arm64 libraries on x86_64 macos, but fortunately, github provided arm-based macos image, with macos-14 image, arm64-based library was successfully compiled.

Thanks for your contributions, I have published v0.6.3 to pub.dev, note the setup.dart was also refactored, now update opencv_dart to v0.6.3 and run dart run opencv_dart:setup macos --arch arm64 to download prebuilt binary and test it.

If you have any problems, you can open an issue or try to fix it and open a new PR.

[TotemaT]

The install and setup went flawlessly, my app built and ran as expected with the new version !

Thanks a lot, I'll let you know if I encounter any issue while using your library 😁