nir/spirv: implement BuiltInWorkDim

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Karol Herbst <kherbst@redhat.com>

src/compiler/spirv/vtn_variables.c

@@ -1208,6 +1208,10 @@ vtn_get_builtin_location(struct vtn_builder *b,
       *location = FRAG_RESULT_STENCIL;
       vtn_assert(*mode == nir_var_shader_out);
       break;
+   case SpvBuiltInWorkDim:
+      *location = SYSTEM_VALUE_WORK_DIM;
+      set_mode_system_value(b, mode);
+      break;
    case SpvBuiltInGlobalSize:
       *location = SYSTEM_VALUE_GLOBAL_GROUP_SIZE;
       set_mode_system_value(b, mode);