clear a warning: variable set but not used

makedefs.c:2125:12: warning: variable 'sum' set but not used
[-Wunused-but-set-variable]
    int i, sum = 0;
           ^
    1 warning generated.

util/makedefs.c

@@ -2122,7 +2122,7 @@ macronamelimit(char *name, int pref)
 void
 do_objs(void)
 {
-    int i, sum = 0;
+    int i, sum UNUSED = 0;
     char *c, *objnam;
     int nspell = 0;
     int prefix = 0;