Update to use .xcframeworks #13
Description
The walkthrough uses fat binaries and the Apple now-supported way to distribute binaries using .xcframeworks. The latest version of the Gigya dependency is also in .xcframework format now instead of the traditional .framework only.
I'd like to submit a PR that updates the build script to build and the dependency to be .xcframeworks.
The corresponding docs issue for this is https://github.com/MicrosoftDocs/xamarin-docs/issues/3547.