OK – so solved it on my own by…
install cocopods
sudo gem install pods
this takes ages – which you already know
change directories to platform/ios
cd platform/ios
run pod install
pod install
change directories back your ionic project
cd ../../
run ios build
ionic cordova build ios
the trick is to open the workspace file - not the project file
Build and Run it on real device from there – there shouldn’t be an error now when you build or archive