it does look confusing when i686 file contains only comment "x86-64 things"
# first platform file entry can't contain regexps
%{_target_cpu}-%{_target_vendor}-linux
-# x86_64 things
%ifarch x86_64
x86_64-[^-]*-[Ll]inux(-gnu)?
amd64-[^-]*-[Ll]inux(-gnu)?
x86_64-[^-]*-[Ll]inux(-gnu)?
%endif
-# x86 things
%ifarch athlon %{x8664}
athlon-[^-]*-[Ll]inux(-gnu)?
%endif
sparc-[^-]*-[Ll]inux(-gnu)?
%endif
-# noarch
noarch-[^-]*-.*
EOF