Use two separate output variables (EntitlementsInExecutable/EntitlementsInSignature)
instead of using the same output variable for two different purposes. This makes
the code more self-explanatory.
Also move the simulator check to the C# code, that way it's easier to re-use elsewhere.
* [msbuild] Share the _CompileEntitlements task.
* [msbuild] Create the same class hierarchy for Xamarin.Mac and Xamarin.iOS for the CompileEntitlements task.
CompileEntitlementsTaskBase
└─── iOS/CompileEntitlementsTaskCore
│ └─── iOS/CompileEntitlements
└─── Mac/CompileEntitlementsTaskCore
└─── Mac/CompileEntitlements
This also means we can remove a known failure in the list of MSBuild tasks that don't
conform to our 'no code in final task implementation' requirements.