When a shader performs a geometry shader injectoin to work around
features that are not supported natively on the GPU (viewport,
barycentric coordinates, layered rendering), linking would fail.
The reason was that the geometry shader was stored in a slot that was
patched by the specialization constants, resulting in an empty geometry
shader. An empty shader can be compiled, but doesn't match the interface
with other stages, so the linking would fail.
This fixes the issue that EEVEE crashed on Intel iGPUs. These GPUs
don't support viewports.
Pull Request: https://projects.blender.org/blender/blender/pulls/117440
cd756143cf