Steps to reproduce:
1. Download attached project
2. Switch platform to UWP
3. Change scripting backend to .NET
4. Build project

Expected results: Build is successful
Actual results: Build fails. The exception is thrown in the Console window
Exception: Assets\JobTest.cs(2,13): error CS0234: The type or namespace name 'Jobs' does not exist in the namespace 'Unity' (are you missing an assembly reference?)

Reproduced with: 2018.3.0a3, 2018.2.0b10, 2018.1.7f1

Not reproducible on mono and IL2CPP Scripting backends

Why by design: we do not support the new Jobs system on .NET scripting backend. We made this design decision consciously for several reasons:

1. .NET scripting backend cannot support several key features that we wanted in the new job system;
2. We knew we were going to deprecate .NET scripting backend soon (it was marked deprecated in Unity 2018.2);
3. We didn't want to compromise the design of our new job system that will be a foundational building block for our future features for years to come in Unity just because .NET scripting backend (which we're about to deprecate) does not work with such design.