[Bug] IOSResolver.dll tries to load on Windows/Linux - causes error

### [REQUIRED] Please fill in the following fields:

* Unity editor version: 2021.3.16f1
* External Dependency Manager version: 1.2.176 (longstanding issue with all previous versions)
* Source you installed EDM4U: .unitypackage (.unitypackage or Unity Package Manager)
* Features in External Dependency Manager in use: Android Resolver (Android Resolver, iOS Resolver, VersionHandler, etc.)
* Plugins SDK in use: none (Firebase, Admob, Facebook, etc.)
* Platform you are using the Unity editor on: Linux (Mac, Windows, or Linux)

### [REQUIRED] Please describe the issue here:

1. Import the .unitypackage into any project and run on Linux (or Windows)
2. Note the following error in the console:

```
Assembly 'Assets/ExternalDependencyManager/Editor/1.2.176/Google.IOSResolver.dll' will not be loaded due to errors:
Unable to resolve reference 'UnityEditor.iOS.Extensions.Xcode'. Is the assembly missing or incompatible with the current platform?
```

#### Please answer the following, if applicable:
What's the issue repro rate? (eg 100%, 1/5 etc)

100%

What happened? How can we make the problem occur?
This could be a description, log/console output, etc.

This is because this DLL can only be loaded on a Mac. I've fixed this manually for some time by changing the Platform Settings for that file from `Any OS` to `macOS`, which updates the meta and prevents issues.

I've put up with this for a while, but now one of my customers asked how to fix the error after importing External Dependency Manager. I think it should be like this by default to prevent confusion.