change the condition to find python interpreter to avoid skipping the find process. (#43888)

* change to condition to find python interpreter to avoid skipping the find process.
PYTHONINTERP_FOUND is the best signal that python interpreter is found.

paddle/phi/api/lib/CMakeLists.txt

@@ -95,7 +95,7 @@ set(wrapped_infermeta_header_file
 set(wrapped_infermeta_source_file
     ${CMAKE_SOURCE_DIR}/paddle/phi/infermeta/generated.cc)
 
-if(NOT PYTHON_EXECUTABLE)
+if(NOT PYTHONINTERP_FOUND)
   find_package(PythonInterp REQUIRED)
 endif()