If you don't mind releasing the source code then the best option is to upload it as a b4xlib. This will be simpler for the developers to use and simpler for you to upgrade.
It is better to add your own prefix to the library, eg: iCKSomething.
It must be a fat binary and include at least: arm64 and armv7. If you want it to be compatible with the simulator then it should also include i386_x64.
Thanks. I think my query comes from my understanding that Apple doesn't like App Store submissions that include x86 binaries. But I guess I can rely on the forum users removing any x86 binaries from the .a file before submission.