update modules

src/pystencilssfg/cmake/FindPystencilsSfg.cmake

@@ -47,6 +47,7 @@ endif()
 
 if(${PystencilsSfg_FOUND})
     message( STATUS "Found pystencils Source File Generator (Version ${PystencilsSfg_VERSION})")
+    message( STATUS "Using Python interpreter ${PystencilsSfg_PYTHON_INTERPRETER} for SFG generator scripts.")
     
     execute_process(COMMAND ${PystencilsSfg_PYTHON_INTERPRETER} -m pystencilssfg cmake modulepath --no-newline
                     OUTPUT_VARIABLE _PystencilsSfg_CMAKE_MODULE_PATH)

src/pystencilssfg/cmake/modules/PystencilsSfg.cmake

@@ -10,7 +10,9 @@ set(PystencilsSfg_GENERATED_SOURCES_DIR "${CMAKE_BINARY_DIR}/sfg_sources" CACHE
 mark_as_advanced(PystencilsSfg_GENERATED_SOURCES_DIR)
 
 #   This cache variable definition is a duplicate of the one in FindPystencilsSfg.cmake
-set(PystencilsSfg_PYTHON_INTERPRETER ${Python_EXECUTABLE} CACHE PATH "Path to the Python executable used to run pystencils-sfg")
+if(NOT DEFINED CACHE{PystencilsSfg_PYTHON_INTERPRETER})
+    set(PystencilsSfg_PYTHON_INTERPRETER ${Python_EXECUTABLE} CACHE PATH "Path to the Python executable used to run pystencils-sfg")
+endif()
 
 file(MAKE_DIRECTORY "${PystencilsSfg_GENERATED_SOURCES_DIR}")