spirv: Create PRIMITIVE_INDICES for NV_mesh_shader on-demand.

The shader can have SpvOpWritePackedPrimitiveIndices4x8NV while the
output variable may not exist. This seems to be a defect in the
NV_mesh_shader SPIR-V spec, let's work around it by creating the
variable on-demand.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15005>
1 file changed