Add a GLSL compiler to improve Shader Management

[JonasGilg]

The Problem

Currently shaders are being build using the compiler of the GPU driver. This leads to missing features and inconsistencies. We are mostly missing #include and proper #define functionality. To circumvent this problem, we currently build the shaders at runtime by stitching a string together.

The Solution

We can use a library, that compiles shaders with all required features. There are two contenders:

• glslang
• libshaderc

Both libraries should be fulfilling our needs and are under active development. glslang has a C++ interface, for which I do prefer it.

Any opinions?