[ 68%] Built target IoSystemCall
Linking C shared library _build/dll/libIoSocket.dylib
Undefined symbols for architecture x86_64:
  "_evbuffer_get_length", referenced from:
      _IoEvOutRequest_RequestDoneCallback in IoEvOutRequest.c.o
  "_evbuffer_copyout", referenced from:
      _IoEvOutRequest_RequestDoneCallback in IoEvOutRequest.c.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make[2]: *** [addons/Socket/_build/dll/libIoSocket.dylib] Error 1
make[1]: *** [addons/Socket/CMakeFiles/IoSocket.dir/all] Error 2