Build a model docs suggested tweaks

[chrisb13]

I was following these docs:
https://access-hive.org.au/models/run-a-model/build_a_model/
and found that some of the instructions felt more complicated than necessary, or lacked small useful details.

When I compiled a fresh version of ACCESS OM3, the executables didn't quite match the paths suggested here ## Output directory for compiled packages (in my case /g/data/tm70/cyb561/spack/0.22/release/linux-rocky8-x86_64/intel-2021.10.0/access-om3-nuopc-git.0.3.1_0.3.1-va553vmg3iv3i7uknyyymh34nna2hz7s/bin/access-om3-MOM6-CICE6).

I also had to guess how to find the hash information (/g/data/tm70/cyb561/spack/0.22/environments/mom6_dev/spack.lock).

Additionally, I think most users will be using the Spack setup instructions so I would suggest the text in the green box goes at the top and the edge cases goes later? (Saves the user having to learn about Spack's complicated directory system unnecessarily.)

This statement is important: The source code is automatically copied inside the environment's folder but could be more explicit, for me it was: /g/data/tm70/cyb561/spack/0.22/environments/mom6_dev/access-om3-nuopc, so adding an example path would help (/g/data/$PROJECT/$USER/spack/0.22/environments/#ENV_NAME/mom5 I think)

[chrisb13]

@anton-seaice also taught me this handy undo process when something goes wrong with one's develop workflow

spack undevelop access-om3-nuopc
#remove access-om3-nuopc from environments folder
spack -d develop [email protected]

Would be worth mentioning undevelop and -d I think

[anton-seaice]

We discovered also that its best if spack develop uses the same version as the version already in the spec for an environment.

See notes here about this (and the alternative which uses the spack change command) : https://github.com/spack/spack/wiki/Telcon:-2024-12-03