make: fix GCC warnings

@@ -860,12 +860,12 @@
  *      sets up dir, following symlinks.
  *      returns zero for success, or
  *      -1 for error (with errno set properly)
  */
 static int
-resolve (char   *indir, /* search directory */
-         char   *cmd,   /* search for name */
+resolve (const char *indir,     /* search directory */
+         const char *cmd,       /* search for name */
          char   *dir,   /* directory buffer */
          char   **run)  /* resultion name ptr ptr */
 {
     char               *p;
     int                 rv = -1;