IMHO it would be very useful to be able to use extended globbing in spec files' %files sections; "shopt -s extglob" does it for bash. ATM it doesn't seem to be possible, as I haven't found a way to put any shell commands into %files sections. If a workaround exists, I'd be grateful to hear about it...
Use "%files -f manifest", and generate the manifest file any way you choose at the end of the %install scriptlet. There's no way to do directly in %files, as this isn't a shell context. If you can map the "shoopt -s extglob" back to the actual C API flags for glob(3) and/or fnmatch(3), I might be able to set that flag by default. Currently rpm has a conservative "0" value for the flags, and a spot check of the available glob flags shows no immediately interesting values.