Blender Git Loki

Added shader compiler abstration.

The shader_compiler is an abstration layer for in case we need to switch
between other shader compilers in the future.

The shader compiler uses a CPP Api as it will only be accessed from GPU
module.

```
const char *source = "#version 450nvoid main() {}";
shader_compiler::Compiler *compiler = shader_compiler::Compiler::create_default();
shader_compiler::Job job;
job.source = source;
job.name = __func__;
job.source_type = shader_compiler::SourceType::GlslComputeShader;
job.compilation_target = shader_compiler::TargetType::SpirV;

shader_compiler::Result *result = compiler->compile(job);
EXPECT_EQ(result->type, shader_compiler::TargetType::SpirV);
EXPECT_EQ(result->status_code, shader_compiler::StatusCode::Ok);
EXPECT_GT(result->bin.size(), 0);
EXPECT_EQ(result->error_log, "");
delete result;
delete compiler;
```

The CMakeFiles need some attention as it currently works when linking to
the shaderlib_combined. On linux it picks up the shaderlib from the
vulkan SDK, eventually it needs to pick up from our prebuild libraries.