The bug

Shader includes located in assets/minecraft/shaders/include/ will fail to compile correctly and cause core shaders that use them to error if there is no newline at the end of the file.

How to reproduce

1. Download the provided resource pack, where only light.glsl is included identical to vanilla but without a newline at the end
2. The game will turn black and the output log will flood with OpenGL errors
3. You can edit light.glsl and add a newline at the end and reload to see that the issue is fixed