Update README about how to get build dependencies

[manodeep]

The README says there are submodules and recommends using git clone --recursive https://github.com/ACCESS-NRI/libaccessom2.git. However, there are no submodules here but there aren't any; and it is unclear how the user is expected to get the dependencies. (This is in contrast to COSIMA/libaccessom2 which does have the dependencies as submodules)

What needs to be fixed:

• Remove the reference to submodules
• Update the recursive clone instruction to a regular clone
• Add instructions on where to get the external dependencies (datetime-fortran, json-fortran, oasis3-mct)

Here's the contents of .git/config showing that there are no submodules:

[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[submodule]
        active = .
[remote "origin"]
        url = https://github.com/ACCESS-NRI/libaccessom2.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
        remote = origin
        merge = refs/heads/master

[aidanheerdegen]

Agreed. The documentation is out of date, and has never been updated to reflect ACCESS-NRI supports building via spack.

This is related to #13 which has some more information.