I have never linked interdependent libraries, but from a Google search I learned the link order of the libraries determines whether the linking works. Add both libraries to your project and see if it links. If it doesn't, change the link order.

You can view the link order from your Xcode project window. Click the disclosure triangle next to Targets in the Groups and Files list to get your project's target. Click the disclosure triangle next to the target to examine the target's build phases. Look at the Link Binaries with Libraries build phase.

For more information on linking with Xcode, look at the January 2007 archive of this blog, which you can find on the right side of the page. There's a post on linking external libraries.