Fix coverity issue

** CID 1598412:  Error handling issues  (CHECKED_RETURN)
/src/parse.c: 273 in main()

________________________________________________________________________________________________________
*** CID 1598412:  Error handling issues  (CHECKED_RETURN)
/src/parse.c: 273 in main()
267                     if (0 == s && ferror(fd))
268                     {
269                             perror("fread " OUTPUT_FILENAME);
270                             return -1;
271                     }
272                     fwrite(buff, s, 1, stdout);
>>>     CID 1598412:  Error handling issues  (CHECKED_RETURN)
>>>     Calling "gzfwrite(buff, s, 1UL, zfd)" without checking return value. This library function may fail and return an error code.
273                     gzfwrite(buff, s, 1, zfd);
274             }
275             fclose(fd);
276             gzclose(zfd);
277
278             /* remove now useless output.txt */

src/parse.c

@@ -270,7 +270,7 @@ int main(int argc, char *argv[])
 			return -1;
 		}
 		fwrite(buff, s, 1, stdout);
-		gzfwrite(buff, s, 1, zfd);
+		(void)gzfwrite(buff, s, 1, zfd);
 	}
 	fclose(fd);
 	gzclose(zfd);