Reproduction steps:
1. Download the "EntityComponentSystemSamples" project from https://github.com/Unity-Technologies/EntityComponentSystemSamples
2. Build "SceneSwitcher" and "HelloCube_05_SpawnFromMonoBehaviour" scenes using IL2CPP scripting backend.
3. Play the build.
4. Check the logs.

Actual behavior:
- The scene doesn't play and errors are shown.
- Some critical parts of the project are stripped when building to IL2CPP.
- I think link.xml file should be updated to prevent stripping.
- The issue is specific to the project and most likely not related to Unity.

Reproduced with:
iOS(IL2CPP) and macOS(IL2CPP)

Not reproducible with:
iOS(Mono) and macOS(Mono)

Error message:
MissingMethodException: Constructor on type 'GameObjectConversionMappingSystem' not found.
at System.RuntimeType.CreateInstanceImpl (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes, System.Threading.StackCrawlMark& stackMark) [0x00000] in <00000000000000000000000000000000>:0
at System.Activator.CreateInstance (System.Type type, System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes) [0x00000] in <00000000000000000000000000000000>:0
at Unity.Entities.World.CreateSystemInternal (System.Type type, System.Object[] constructorArguments) [0x00000] in <00000000000000000000000000000000>:0
at Unity.Entities.World.CreateSystem[T] (System.Object[] constructorArgumnents) [0x00000] in <00000000000000000000000000000000>:0
at Unity.Entities.GameObjectConversionUtility.CreateConversionWorld (Unity.Entities.World dstEntityWorld, Unity.Entities.Hash128 sceneGUID, Unity.Entities.GameObjectConversionUtility+ConversionFlags conversionFlags) [0x00000] in <00000000000000000000000000000000>:0
at Unity.Entities.GameObjectConversionUtility.ConvertGameObjectHierarchy (UnityEngine.GameObject root, Unity.Entities.World dstEntityWorld) [0x00000] in <00000000000000000000000000000000>:0
at Samples.HelloCube_05.HelloSpawnMonoBehaviour.Start () [0x00000] in <00000000000000000000000000000000>:0