configure llvm fail. Host Clang must be able to find libstdcxx4.7 or newer - cmake

Question

my project depends on llvm+clang+cmake.I use ninja to make compile simple.
my OS is : OS X Yosemite(10.10.5).here is how the error occurs.
1) get llvm&clang
$ mkdir ~/clang-llvm && cd ~/clang-llvm
$ git clone http://llvm.org/git/llvm.git
$ cd llvm/tools
$ git clone http://llvm.org/git/clang.git
$ cd clang/tools
$ git clone http://llvm.org/git/clang-tools-extra.git extra
2) install CMake and Ninja
$ cd ~/clang-llvm
$ git clone https://github.com/martine/ninja.git
$ cd ninja
$ git checkout release
$ ./bootstrap.py
$ sudo cp ninja /usr/bin/
$ cd ~/clang-llvm
$ git clone git://cmake.org/stage/cmake.git
$ cd cmake
$ git checkout next
$ ./bootstrap
$ make
$ sudo make install
3)compile ninja
$ cd ~/clang-llvm
$ mkdir build && cd build
$ cmake -G Ninja ../llvm -DLLVM_BUILD_TESTS=ON # Enable tests; default is off.
$ ninja
$ ninja install
4)config clang
$ cd ~/clang-llvm/build
$ ccmake ../llvm
after that , I get into the advanced mode (by press t)
CMAKE_CXX_COMPILER：*I change it to clang++*
CMAKE_C_COMPILER：*I change it to clang*
LLVM_ENABLE_EH and LLVM_ENABLE_RTTI： *I change it from OFF to ON*
and then I press c to configure. error happens.ERROR is :
**CMake Error at cmake/modules/HandleLLVMOptions.cmake:43 (message):
Host Clang must be able to find libstdc++4.7 or newer!
Call Stack (most recent call first):
CMakeLists.txt:358 (include)**
Any ideas?
Thanks