How to reproduce:
1. Open the "Shader repro.zip" project
2. Build the project, it should fail. If the build succeeds, close the project and open it again.
3. Build the project, it succeeds

Actual result: Build fails with shader errors until you move the shaders folder somewhere and back to original location.
Expected result: Build should succeed for the first time.

Reproducible with: 2017.2.3f1, 2017.4.1f2, 2018.1.0f2, 2018.2.0b1.
Not Reproducbile with: 2017.4.3f1, 2018.2.0b4. 2018.2.0b2.

Note:
The user said deleting Library folder fixes the problem temporarily, but for me, it didn't solve the problem. (2017.4.1f1)
In 2017.4.1f1, the build fails until changing the location of the uRaymarching folder and placing it back.