OSX: Adding more dependencies

[fangohr]

• adding more dependencies is more demanding as we need to see if the dependencies compile fine on OSX
• we first run the default variants (spack install octopus) - this gives us a useful data point
• we then try to compile another version with additional dependencies
• tests of octopus we do before we compile the second version (otherwise we would need to specify which octopus version we want)

[iamashwin99]

Closing as this is too outdated. Might want to revisit supporting osx at a later point.