Updates for fnal-wn-el9 container

[vitodb]

The proposed updates allow the fnal-wn-el9 container to be built. This includes changes for singularity to apptainer transition, but more changes could be required for a full transition.

[mambelli]

Vito, do we need a custom apptainer configuration? Could/should that file be removed or reduced? Should we check w/ Dave?

[vitodb]

Vito, do we need a custom apptainer configuration? Could/should that file be removed or reduced? Should we check w/ Dave?

I think better to check with Dave. Because recently started the migration from singularity to apptainer I thought this could be a good time to have the EL9 container with use of apptainer configurations.

One tricky thing seems to be this code block that I'm not sure if it has an apptainer equivalent.

[vitodb]

@DrDaveD in this PR we are setting up an Alma9 Docker container that is converted as singularity container and used by users to run grid jobs. The Dockerfile used to install singularity and related setup to allow users to start another container inside this one. We are thinking to replace the singularity setup inside the container with an equivalent apptainer setup. Other than the standard singularity config file we also have some other dedicated setup. We would be grateful if you can help to transition the singularity setup to the apptainer setup.

[DrDaveD]

It's not a good idea to completely replace apptainer.conf, as the default contents keep changing. I doubt there's any default value that you need to change, so I recommend just dropping it.

If there is a value you need to change, I recommend using apptainer config global --set to set a new value.

[mambelli]

Merged to have a working EL9 WN. I opened #17 to review singularity/apptainer setup on all containers.