`CMAKE_GUARD "SUPERLU_FOUND OR SuiteSparse_UMFPACK_FOUND"` fails even though both are installed

From the CI system:

Name:      pthreaddirectamgtest
FullName:  ./dune/istl/paamg/test/pthreaddirectamgtest
Status:    NOTRUN
Output:
           This test was skipped because it failed the following CMake Conditions:
             SUPERLU_FOUND OR SuiteSparse_UMFPACK_FOUND

But I just installed both libsuperlu-dev and libsuitesparse-dev in the CI environment which enabled the other tests using SuperLU or SuiteSparse (compare https://gitlab.dune-project.org/core/dune-istl/builds/589 and https://gitlab.dune-project.org/core/dune-istl/builds/592).

Maybe @dominic knows why this condition fails?