glsl/shader_enums: Add the other two compute builtins

These weren't added before because they are actually calculated values that
are computed from other inputs.  However, in order to handle them in
nir_lower_system_values, it's nice for them to have a cannonical locaiton.

Reviewed-by: Rob Clark <robdclark@gmail.com>

src/compiler/shader_enums.h

@@ -459,6 +459,8 @@ typedef enum
     */
    /*@{*/
    SYSTEM_VALUE_LOCAL_INVOCATION_ID,
+   SYSTEM_VALUE_LOCAL_INVOCATION_INDEX,
+   SYSTEM_VALUE_GLOBAL_INVOCATION_ID,
    SYSTEM_VALUE_WORK_GROUP_ID,
    SYSTEM_VALUE_NUM_WORK_GROUPS,
    /*@}*/