libcatalyst downloads source during test

[wspear]

@mathstuf In its compile phase the libcatalyst test attempts to git clone a repository to obtain test code. This isn't allowed since some systems (i.e. crusher) do not have external network access on compute nodes there the testsuite will be run.

[mathstuf]

Is there some bit we can check to see if network access works? I suppose we can check the return code of git clone and skip those parts as needed.

[mathstuf]

spack/spack#40112 adds the test here as part of the Spack package itself (where the source tree is still around). Is that sufficient to test Catalyst? Or do we still want a way to test it on deployments separately?