make: unifdef for other OSes (undefined)

*** 52,66 ****
                  char    *ran_name;      /* symbol defined by */
          }       ran_un;
          off_t   ran_off;                /* library member at this offset */
  };
  
- #if defined(linux)
- #include <ctype.h>              /* isspace */
- #else
  #include <unistd.h>             /* close() */
- #endif
  
  
  /*
   * Defined macros
   */
--- 52,62 ----