Undefined Symbol for Architecture i386 “_CloseZStream”, “_CreateZStream” etc

I have build the Unity project on my mac and it opens in XCode, it tries to build it straight away. Then it tells me it fails with 201 errors all linker errors. Error is: Undefined symbols for architecture i386: "_CloseZStream", referenced from: _DeflateStream_CloseZStream_m4_604 in Bulk_System_0.o (maybe you meant: _DeflateStream_CloseZStream_m4_604)

Has anyone got any ideas on how this problem can be fixed.

Many thanks in advance