To reproduce:
1. Open project attached by the user
2. Attach "Main" scene in build settings and build project (iOS platform)
3. Open built project in XCode and run it on a device
4. Inspect the console in Xcode

Expected result: There shouldn't be any exceptions when unloading domain
Actual: NotSupportedException: /Users/builduser/buildslave/unity/build/External/il2cpp/il2cpp/libil2cpp/icalls/mscorlib/System/AppDomain.cpp(196) : Unsupported internal call for IL2CPP:AppDomain::InternalUnload - "This icall is not supported by il2cpp."

Reproduced with: 2017.1.1p3, 2017.2.0f2, 2017.3.0b3
Device: iPhone 6s iOS 11.0

5.6.3p4 version failed building project in Xcode, "No member named 'Configuration' in namespace 'il2cpp::icalls::System'"

BY DESIGN: Unity does not support multiple app domains with IL2CPP, so this is the expected behavior.