tests/shader-runner: Make geometry shaders optional.
This allows the Vulkan runner to execute in environments which do not support geometry shaders, most notably MoltenVK. In particular, that enables SM<4 shaders to run in such environments
This allows the Vulkan runner to execute in environments which do not support geometry shaders, most notably MoltenVK. In particular, that enables SM<4 shaders to run in such environments