Fix issue #200 (python wrapper compilation error for macOS clang).

wrapper/python/src/FaustCoreCpp.h

@@ -69,12 +69,14 @@ class FaustCoreCpp
      *
      * \return true to indicate the two objects are different.
      */
+#ifdef USE_GPU_MOD
     bool make_transform(Faust::TransformHelper<FPP, GPU2>**) const;
     /**
      * Copies the pointer of the underlying transform into the argument.
      *
      * \return false to indicate the two objects are the same.
      */
+#endif
     bool make_transform(Faust::TransformHelper<FPP, Cpu>**) const;
     void Display() const { transform->display();}
     const char* to_string() const;

wrapper/python/src/FaustCoreCpp.hpp

@@ -710,12 +710,14 @@ bool FaustCoreCpp<FPP,DEV>::make_transform(Faust::TransformHelper<FPP,Cpu>** th)
     return false;
 }
 
+#ifdef USE_GPU_MOD
 template<typename FPP, FDevice DEV>
 bool FaustCoreCpp<FPP, DEV>::make_transform(Faust::TransformHelper<FPP,GPU2>** th) const
 {
     *th = new Faust::TransformHelper<double,GPU2>(*this->transform);
     return true;
 }
+#endif
 
 template<typename FPP, FDevice DEV>
 FaustCoreCpp<FPP,DEV>::~FaustCoreCpp()