Sample ContextScreenManager missing namespace error

[trdillon]

Using the provided Samples in the 1.2.0 version of the package can cause a missing namespace error when attempting to build the project.

Assets\Samples\iOS 14 Advertising Support\1.2.0\01 Context Screen\Scripts\ContextScreenManager.cs(4,19): error CS0234: The type or namespace name 'iOS' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)

This seems to be caused by the import using UnityEngine.iOS; not being wrapped in a #if UNITY_IOS directive.

Adding the iOS module to the Unity install resolves this, but this isn't possible or desirable in some situations.