intel/compiler: mark debug constant as const

Should quiet Coverity's "'Constant' variable guards dead code".

Signed-off-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6126>

src/intel/compiler/brw_interpolation_map.c

@@ -89,7 +89,7 @@ brw_setup_vue_interpolation(struct brw_vue_map *vue_map, nir_shader *nir,
       }
    }
 
-   bool debug = false;
+   const bool debug = false;
    if (debug) {
       fprintf(stderr, "VUE map:\n");
       for (int i = 0; i < vue_map->num_slots; i++) {