add test for scotch

Summary

This MR adds a test scotchtest.cc to check that scotch is found and works correctly. The actual scotch test just runs a few standard functions to create a graph and check it validity. The test is added to test the cmake find-package FindPTScotch.cmake and its add_dune_ptscotch_flags macro.

added 1 commit

• b4ad6e23 - cleanup cmake files

Compare with previous version

added buildsystem label

Looks okay, but please squash the commits before merging.

It is marked for Commit-squashing already.

merged

mentioned in commit c166f8d2

mentioned in issue #199 (closed)