There seems to be a zlib dependency during the default build process of OGRE.
Although CMake is able to find a universal binary for zlib installed on my machine, it does not include it in the linker arguments because OGRE_CONFIG_ENABLE_ZIP defaults to off. However, OgreDeflate.cpp has a dependency on ZLib and is compiled regardless of any of the settings.
OS X 10.7
Intel Core 2 Duo