put if statement back that sets PYTHON_INSTDIR

scripts/CMakeLists.txt

@@ -108,6 +108,14 @@ if (DO_PYTHON_BINDINGS)
             PREFIX ""
             LIBRARY_OUTPUT_DIRECTORY "${openbabel_SOURCE_DIR}/scripts/python/openbabel/"
             SUFFIX .so )
+	if( "${PYTHON_INSTDIR}" STREQUAL "" )
+          execute_process(
+            COMMAND
+           ${PYTHON_EXECUTABLE} -c "import sysconfig; print(sysconfig.get_path('platlib', vars={'base': '${CMAKE_INSTALL_PREFIX}'}))"
+            OUTPUT_VARIABLE PYTHON_INSTDIR
+            OUTPUT_STRIP_TRAILING_WHITESPACE
+          )
+        endif()
         if(NOT BINDINGS_ONLY)
             add_dependencies(bindings_python openbabel)
         endif()