In Debian, the attached patch was applied to achieve the following:
FreeOrion fails to build from source on big-endian systems. This patch omits
the endianess and size checks to make the game at least compile on
architectures like s390x. However it cannot be guaranteed anymore that
savegames are portable between different architectures. This is a compromise
for now and needs further testing and feedback from the community.
See also http://www.freeorion.org/forum/viewtopic.php?f=24&t=7550 for a
discussion on this topic.