Support pmix from conda-forge?

[leofang]

xref: https://github.com/conda-forge/openmpi-feedstock/pull/175/files#r1777831382

[jakirkham]

It looks like there are references to openpmix and prrte in the recipe

openmpi-feedstock/recipe/meta.yaml

Lines 59 to 61 in fb069e1

	host:
	#- openpmix
	#- prrte

openmpi-feedstock/recipe/meta.yaml

Lines 68 to 71 in fb069e1

	run:
	- mpi 1.0 openmpi
	#- openpmix
	#- prrte

Appears these were added as commented in PR: #128

There is some discussion in that PR, which could be relevant to uncommenting these