MDL shader uniform block reflection inconsistency

[kwokcb]

Difference

For the supplied code generators only MDL does not seem to provide uniform information for the pixel stage. All GLSL variants (GLSL, ESSL, Vulkan), Metal, and OSL return information.

Reproducible Case

Given a generated shader (say from generateShader.py script)

 for i in range(0, shader.numStages()):
        stage = shader.getStage(i)
        if stage:
            stageName = stage.getName() 
            theBlocks = stage.getUniformBlocks()
            if len(theBlocks) == 0:
                print(f'stage: {stageName} has no uniform blocks')