clingo-cffi unit tests are running on the original concretizer #21912
Description
#20657 added updates to support clingo-cffi. The new Github Action job though is using the original concretizer, since the
environment variable SPACK_TEST_SOLVER is not set to clingo. This can be verified by the log of successful tests:
which reports XFAILs that are expected on the original concretizer.