make: fix GCC warnings

@@ -337,11 +337,11 @@
          * Only prepend the /usr/bin/nice command to the original command
          * if the nice priority, nice_prio, is NOT zero (0).
          * Nice priorities can be a positive or a negative number.
          */
         if (nice_prio != 0) {
-                argv[argv_index++] = NOCATGETS("nice");
+                argv[argv_index++] = (char *)NOCATGETS("nice");
                 (void) sprintf(nice_prio_buf, NOCATGETS("-%d"), nice_prio);
                 argv[argv_index++] = strdup(nice_prio_buf);
         }
         argv[argv_index++] = shellname;
 #if defined(linux)