Scons: Fix usage of CXXFLAGS and CPPFLAGS
Scons: Fix usage of CXXFLAGS and CPPFLAGS

* These were added to CCFLAGS which is incorrect, now are added
  to the proper Scons environment.

* Since after we switched from C++-ish to C11, this is wrong and
  could cause errors when CXXFLAGS contained stuff not allowed
  for C compilation.

kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka