OS-X 10.7 and XCode 4.1 fails

Hey All!
Like many I am getting introduced to IO via the Seven Languages book. Also like a few of you I am having compilation issues. Any ideas on this?

I did 
git clone https://github.com/stevedekorte/io.git
cd io
mkdir build
cd build
cmake ..
make

and got:

Linking CXX shared library _build/dll/libIoObjcBridge.dylib
Undefined symbols for architecture x86_64:
  "_IoSocketInit", referenced from:
      _IoLanguageStateBindingsInitCallback in IoLanguage.m.o
  "_IoSystemCallInit", referenced from:
      _IoLanguageStateBindingsInitCallback in IoLanguage.m.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make[2]: *** [addons/ObjcBridge/_build/dll/libIoObjcBridge.dylib] Error 1
make[1]: *** [addons/ObjcBridge/CMakeFiles/IoObjcBridge.dir/all] Error 2