Hands-on CXX language needed by Pybind11

With PDI installed with Pybind, when calling cmake in hands-on error occurs:

-- Performing Test HAS_CPP14_FLAG
CMake Error at /usr/share/cmake-3.10/Modules/CheckCXXSourceCompiles.cmake:97 (try_compile):
  Unknown extension ".cxx" for file
    /home/sierot/Workspace/PDI-hands-on/build/CMakeFiles/CMakeTmp/src.cxx
  try_compile() works only for enabled languages.  Currently these are:
    C

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