add pmix v4

[xpillons]

The CycleCloud slurm project build slurm with pmix in /opt/pmix/v4 and is expecting it there see the build script.

PMIX is not part of the HPC images and need to be added, it would be great to add it by default.

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1. Add pmix in Ubuntu/Alma HPC images

[marconetto]

is there any plan to have an updated version of images with pmix added into them?

[ltalirz]

I can't find pmix in the codebase of this repository.
Is it installed as a dependency of some other package?

I see that cyclecloud-slurm installs it from source
https://github.com/Azure/cyclecloud-slurm/blob/e877f657e0e4ff0e412804ef81073e02e25edb81/util/build-slurm.sh#L70-L97

Should I open a PR that just copies this function and adds pmix v4?
Not quite sure how to avoid installing v3, but perhaps that is not necessary...

[jithinjosepkl]

We are moving to spack, and will add it through spack from next release onwards.

[tbugfinder]

Is there an issue which provides more details about the spack approach ?

[LiquidPT]

We've moved away from spack, but have added pmix v4.its checked into master and will be in the upcoming release

[LiquidPT]

PMIX v4 has been added to the scripts and will be in the upcoming image release

#329