RecordBinaryComparator should check endianness when compared by long

If the architecture supports unaligned or the offset is 8 bytes aligned, RecordBinaryComparator compare 8 bytes at a time by reading 8 bytes as a long. Otherwise, it will compare bytes by bytes. 

However, on little-endian machine,  the result of compared by a long value and compared bytes by bytes maybe different. If the architectures in a yarn cluster is different(Some is unaligned-access capable while others not), then the sequence of two records after sorted is undetermined, which will result in the same problem as in https://issues.apache.org/jira/browse/SPARK-23207