// Prior to Go1.8, the Writer had a bug where it would output
			// an invalid tar file in certain rare situations because the logic
			// incorrectly believed that the old GNU format had a prefix field.
			// This is wrong and leads to an output file that mangles the
			// atime and ctime fields, which are often left unused.
			//
			// In order to continue reading tar files created by former, buggy