AddPTScotchFlags never called

There is an AddPTScotchFlags.cmake but it's never called/used anywhere. I need to find PTScotch in a downstream module. What's the correct fix?

@simon.praetorius you probably know best?

There is a line in config.h.cmake

/* Define to 1 if PT-Scotch is available */
#cmakedefine HAVE_PTSCOTCH 1

But this seems to be never true because HAVE_PTSCOTCH is never set.