main_cp.c: Ignore return value from stat()

Original author: rlong

CID 26051: Unchecked return value from library in main_cp().

257                        if (Rflag && (Lflag || Hflag))
   CID 26051 (#1 of 1): Unchecked return value from library (CHECKED_RETURN)34. check_return: Calling stat(*argv, &tmp_stat) without checking return value. This library function may fail and return an error code. [Note: The source code implementation of the function has been overridden by a builtin model.]
258                                stat(*argv, &tmp_stat);