https://bugzilla.redhat.com/show_bug.cgi?id=827167
--- Comment #8 from Brendan Jones brendan.jones.it@gmail.com ---
Look here: http://fedoraproject.org/wiki/Packaging:DistTag#Conditionals
You could try something like
%ifarch x86 %define nostack %{?el6: -fno-stack-protector} %endif
CFLAGS="%optflags %{?nostack}"