[cmake] bugfix in python metadata generation
Due to a typo in the check for the existence of HAVE_DUNE_FOO variables, these were falsely reported as undefined and were thus missing in the metadata.
this is a follow-up of !1074 (merged)
Due to a typo in the check for the existence of HAVE_DUNE_FOO variables, these were falsely reported as undefined and were thus missing in the metadata.
this is a follow-up of !1074 (merged)