How to reproduce:
1. Open users attached project and "main" scene
2. Press one of the "Execute" buttons, notice that System.ValueTuple successfully returns string values
3. Go to File --> Build Settings --> Player Settings --> Other Settings
4. Choose Mono as Scripting Backend
5. Build & Run player, once built press one of the "Execute" buttons

Expected result: System.ValueTuple successfully returns string values, just like in Editor
Actual result: System.BadImageFormat or System.TypeInitializationException exceptions are thrown

Reproducible with - 2017.3.0b10, 2017.2.0f3, 2017.2.0a1
Not reproducible with - 2018.1.0a5

Note: Works fine on built player that has IL2CPP (Android) built player