Use -m64 gcc option to enforce 64-bit build regardless of the environment. (#568)
Use -m64 gcc option to enforce 64-bit build regardless of the environment. (#568)

fixes https://github.com/hazelcast/hazelcast-cpp-client/issues/567
hazelcast/hazelcast-cpp-client,hazelcast/hazelcast-cpp-client,hazelcast/hazelcast-cpp-client,hazelcast/hazelcast-cpp-client