Setting build options for OM3

Hi @anton

I’ve finished with the ACCESS rAM3 flagship for a while, so now I have time to get back to this.

I’ve create a PR from GitHub - ACCESS-NRI/ACCESS-OM3 at om3-mom6-debug-example.

The CI failed though. Om3 mom6 debug executable by Rush74 · Pull Request #128 · ACCESS-NRI/ACCESS-OM3 · GitHub

I had to manually resolve config/versions.json and spack.yaml and its probably the latter that is causing problems.

Hoping you can help.