UFunctions using the exec specifier are recognized by UHT when building for Development even if they are in a #if WITH_ENGINE

If a user declares a UFunction with the exec specifier, the UHT will add a call to that function so that it can be used as a console command in the editor. This becomes an issue when the declaration of that UFunction is part of a #if WITH_EDITOR block. When building in Development, the declaration will be skipped by the compiler but the function will still be called in the .generated.h.

1. Create a new blank C++ project
2. Add a new C++ class through the editor (File > New C++ Class...) and add an Actor called MyActor
3. After Visual Studio appears, in the MyActor.h add the following code:

 #if WITH_EDITOR
	UFUNCTION(exec)
		void TestFunction();
#endif 

4. At the top of Visual Studio, use the drop down to change the build configuration from Development Editor to Development.
5. Compile (ctrl+shift+b)
Result: The compile fails with a message mentioning that the function isn't part of AMyActor.
Expected: The UHT should ignore the declaration in the #if WITH_EDITOR to avoid causing compilation errors