Steps to reproduce:
1. Open attached project(link in the description) OR download holo-toolkit project https://github.com/Microsoft/HoloToolkit-Unity
2. Open build settings and switch platform to WSA Universal 10 SDK
3. Open player settings and select IL2CPP scripting backend
4. Build for WSA Universal 10
*build fails with errors as expected*
5. Open player settings and select .NET scripting backend
4. Build for WSA Universal 10

Expected result: build succeeds
Actual result: build fails with errors as if it was built with il2cpp scripting backend

Workaround: create a new c# script to trigger recompilation

Reproducible with: 5.5.2f1, 5.6.0p1, 2017.1.0b1