Allow to build on s390_64
Allow to build on s390_64

Motivation:

It is not possible to build Netty on an s390_64 platform.

Modifications:

Modify pom.xml so that s390_64 is acceptable as os.detected.arch.

Result:

Netty can be built on an s390_64 platform.

Signed-off-by: Tatsushi Inagaki <d275e2ddef1ea9d1d5759b035b351061bdc43719@jp.ibm.com>

gerdriesselmann/netty,gerdriesselmann/netty,gerdriesselmann/netty,gerdriesselmann/netty,gerdriesselmann/netty