Automate iOS builds

Write a new script that performs steps mentioned in [iOS-BUILD.md](https://github.com/UnfoldedInc/deck.gl-native-dependencies/blob/master/docs/iOS-BUILD.md), which could then be called from [build.sh](https://github.com/UnfoldedInc/deck.gl-native-dependencies/blob/master/build.sh)