update build system to make it auto-adapt to include python support or not into MLIAP

src/PYTHON/python_impl.cpp

@@ -26,7 +26,7 @@
 #include <cstring>
 #include <Python.h>  // IWYU pragma: export
 
-#ifdef LMP_MLIAPPY
+#ifdef MLIAP_PYTHON
 #include "mliap_model_python.h"
 // The above should somehow really be included in the next file.
 // We could get around this with cython --capi-reexport-cincludes
@@ -58,14 +58,14 @@ PythonImpl::PythonImpl(LAMMPS *lmp) : Pointers(lmp)
   // one-time initialization of Python interpreter
   // pyMain stores pointer to main module
   external_interpreter = Py_IsInitialized();
-  
-  #ifdef LMP_MLIAPPY
+
+#ifdef MLIAP_PYTHON
   // Inform python intialization scheme of the mliappy module.
   // This -must- happen before python is initialized.
   int err = PyImport_AppendInittab("mliap_model_python_couple", PyInit_mliap_model_python_couple);
   if (err) error->all(FLERR,"Could not register MLIAPPY embedded python module.");
-  #endif
-  
+#endif
+
   Py_Initialize();
   PyEval_InitThreads();