Steps to reproduce:
1. Open the attached project
2. Go to build settings
3. Make sure that:
3.1. Platform is PC, Mac & Linux standalone
3.2. Target platform is Linux
3.3. Architecture is x86_64
4. Build the project

Expected: the project is successfully built
Actual: "error CS0103: The name `VRSettings' does not exist in the current context" is shown

Reproduced on: 5.5.0p4
Not reproduced on: 5.6.0b3
Unable to repro: 5.4.4f1 (freezes on build)
OS: OSX 10.11.6

Note: you can also enter the play mode in the editor at first, but after the build attempt it asks you to correct all of the compile errors.
Note #2: issue occurrs with VRDevice and VRStats class too.