make: fix GCC warnings

*** 860,871 ****
   *      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 */
           char   *dir,   /* directory buffer */
           char   **run)  /* resultion name ptr ptr */
  {
      char               *p;
      int                 rv = -1;
--- 860,871 ----
   *      sets up dir, following symlinks.
   *      returns zero for success, or
   *      -1 for error (with errno set properly)
   */
  static int
! 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;