Based on build logs, xulrunner-python is not built with $RPM_OPT_FLAGS. See bug 496968 for more info.
This bug appears to have been reported against 'rawhide' during the Fedora 13 development cycle. Changing version to '13'. More information and reason for this action is here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping