Created by: backyes

PR for issue https://github.com/baidu/Paddle/issues/297

• the issue that find_package(PythonLibs 2.7 REQUIRED) and find_package(PythonInterp 2.7 REQUIRED) could find different python is BUG in CMAKE, instead of PaddlePaddle. Related BUGs:

http://public.kitware.com/pipermail/cmake/2015-December/062387.html
https://cmake.org/Bug/view.php?id=14809
https://cmake.org/Bug/view.php?id=13794
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=677598
https://github.com/Valloric/YouCompleteMe/issues/1307

But, the solution is not clear.

Solution I prefer:

• Set CMake min version to 3.2 in CMakeList.txt

 cmake_minimum_required(VERSION 3.2) 

• use CMAKE_PREFIX_PATH= to restrict python selection in external compiling script, instead of hacking CMakeList.txt

@emailweixu if you feel free, can verify the following solution in your test environment.

cmake_minimum_required(VERSION 3.2) 

How about your suggestions. @reyoung @emailweixu @wangkuiyi