nir/linker: take into account hidden uniforms

So they are not exposed through the introspection API.

It is worth to note that the number of hidden uniforms of GLSL linking
vs SPIR-V linking would be somewhat different due the differen order
of the nir lowerings/optimizations.

For example: gl_FbWposYTransform. This is introduced as part of
nir_lower_wpos_ytransform. On GLSL that is executed after the IR-based
linking. So that means that on GLSL the UniformStorage will not
include this uniform. With the SPIR-V linking, that uniform is already
present, but marked as hidden. So it will be included on the
UniformStorage, but as hidden.

One alternative would create a special how_declared for that case, but
seemed an overkill. Using hidden should be ok as far as it is used
properly.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/compiler/glsl/gl_nir_linker.c

@@ -56,6 +56,10 @@ nir_build_program_resource_list(struct gl_context *ctx,
    for (unsigned i = 0; i < prog->data->NumUniformStorage; i++) {
       struct gl_uniform_storage *uniform = &prog->data->UniformStorage[i];
 
+      /* Do not add uniforms internally used by Mesa. */
+      if (uniform->hidden)
+         continue;
+
       if (!link_util_add_program_resource(prog, resource_set, GL_UNIFORM, uniform,
                                           uniform->active_shader_mask)) {
          return;