CI: gmsh clones are failing

In the latest self-hosted CI run the clone from gmsh failed which caused all builds/tests to be skipped.  

https://github.com/SCOREC/omega_h/actions/runs/20177822360/job/57930332434#step:4:2721

I think we should install gmsh locally (via spack?) and avoid the clone and build.  I don't think it is critical that we test against the latest/greatest gmsh version.
