rsvndump 0.5.6-1 is not built with $RPM_OPT_FLAGS, see the gcc lines in the build log: http://kojipkgs.fedoraproject.org/packages/rsvndump/0.5.6/1.fc16/data/logs/x86_64/build.log 0.5.5-1 did not have this problem.
Thanks Ville, fixed in rsvndump-0.5.6-2.fc16.