By default, CMake assumes both a C and C++ compiler are required.
This is not needed for mraa because it only provides C++ header
files. Note that if using SWIG you need one and if using node.js 3+ you'll need
a C++11 compiler
Signed-off-by: Pieterjan Camerlynck <pieterjan.camerlynck@gmail.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>