Build 3D Slicer for MacOS arm64?

@GeneRisi There are some various scripts around that people have tried to build Slicer from source to build a ARM64 variant, but nothing official yet such as Slicer preview build of such a version.

The below issue is still in progress and various Slicer developers have been actively working on a long chain of dependency updates including Qt5 → Qt6 that is part of bringing in ARM64 support across all the various libraries that Slicer uses. It is currently being worked on and I expect it to continue for a month or two.