xcode 5 compile for arm64 iPhone failed

I am now building a C++ library for iPhone with xcode 4. When I build the architecture "armv7","armv7s" and "i386", everything is fine. But when I want to build for the architecture of "arm64", I have:

 C++ Compiler:                CMAKE_CXX_COMPILER-NOTFOUND  (ver 5.1.0)

It seems that it cannot find the c++compiler. By the way, I am now using cmake toolchain to build the library, and more detailed error messages are as follows:

-- Setting up iPhoneOS toolchain
-- iPhoneOS toolchain loaded
-- The CXX compiler identification is Clang 5.1.0
-- The C compiler identification is Clang 5.1.0 
CMAKE_LIBRARY_PATH=/lib;/usr/lib
-- Looking for linux/videodev.h
CMake Error at /Applications/CMake http://ift.tt/1G0YvVt (get_filename_component):
  get_filename_component called with incorrect number of arguments
Call Stack (most recent call first):
  CMakeLists.txt:3 (PROJECT)


CMake Error: Internal CMake error, TryCompile configure of cmake failed

-- Looking for linux/videodev.h - not found
-- Looking for linux/videodev2.h
CMake Error at /Applications/CMake http://ift.tt/1G0YvVt (get_filename_component):
  get_filename_component called with incorrect number of arguments
Call Stack (most recent call first):
  CMakeLists.txt:3 (PROJECT)


CMake Error: Internal CMake error, TryCompile configure of cmake failed

Any ideas? Thanks.