Verify initial `spack.yaml`

[CodeGat]

This spack.yaml comes from https://github.com/COSIMA/spack-config/blob/0.21.2/environments/access-om3-0_x_0/spack.yaml

Verify that it is installable and that no changes need to be made - for example:

• versioning the overall access-om3 deployment. Will versioning information be within the spack.yaml, as it is done in ACCESS-OM2?

[CodeGat]

This was done during the creation of the spack.yaml in #5
I've installed access-om3 as part of that spack.yaml and verified that it works