OpenGL Renderer: use shaders cross-compiler

Source code compilers:

• glslang and SPIRV-Cross
  • We should check if it supports compilation from HLSL to SPIR-V for OpenGL. (https://github.com/KhronosGroup/glslang/issues/1417)
  • shaderc
• DirectXShaderCompiler and SPIRV-Cross
  • ShaderConductor
• vkd3d-shader
• hlsloptconv (HLSL Optimizing Converter, SM3.0 – SM4.0)
• hlslparser
  • HLSLParser (Only SM3.0, no preprocessor, so doesn't support #includes)
• hlsl2glslfork (Only SM3.0)
• shgen
• XShaderCompiler (SM4 – SM5) (won't work for us currently, see https://github.com/LukasBanana/XShaderCompiler/issues/98)
• https://zz85.github.io/hlslparser/
• https://github.com/DiligentGraphics/DiligentCore/tree/master/Graphics/HLSL2GLSLConverterLib
  • https://diligentgraphics.com/diligent-engine/shader-converter/
  • http://diligentgraphics.com/diligent-engine/shader-converter/supported-features/
  • https://www.gamedeveloper.com/programming/state-of-the-art-hlsl-to-glsl-converter

Bytecode compilers are not suitable, we need to compile from sources.
However, here's the list of some bytecode compilers:

• HLSLCrossCompiler
  • Amazon's Lumberyard version
  • Unity's HLSLcc
• DXVK's DXBC reader – Supports SM 4.0 through SM 5.0.
• mojoshader – Supports SM 1.0 through SM 3.0
  • https://github.com/espes/mojoshader – fork

Other useful links:
Decompilers:

• https://github.com/etnlGD/HLSLDecompiler
• https://github.com/luxuia/dxbc_reader
• https://github.com/AndresTraks/HlslDecompiler/
• https://gitlab.winehq.org/fcasas/binary-d3dbc-parser

Other projects:

• https://github.com/felipeagc/tinyshader
• https://github.com/shader-slang/slang
• https://github.com/septag/glslcc
• https://github.com/julianrendell/GLSL2HLSL
• https://github.com/Kode/krafix
• https://github.com/KTXSoftware/kfx
• https://github.com/MicrosoftEdge/WebGL/tree/master/GLSLParse
• https://github.com/zigguratvertigo/hlsl-to-ispc
• https://github.com/mellinoe/ShaderGen
• https://github.com/DragonJoker/ShaderWriter
• https://github.com/polymonster/pmfx-shader
• https://github.com/cezbloch/shaderator

Playground, testing, live coding:

• https://github.com/tgjones/shader-playground
• https://github.com/astralis3d/HLSLexplorer
• https://github.com/atyuwen/hlsl_live_coding

Other suggestions?

This issue is a sub-task of #280

Start with the requirements in this issue and its parent task #280, then evaluate the listed source-code shader compilers for HLSL-to-SPIR-V and OpenGL support. Done requires a decided cross-compiler approach and a defined integration path, but no repository files or tests are named here.