external PRRTE library alongside external PMix?

[Drew Parsons <dparsons@debian.org>]

Hi Alastair
(and cc: Debian Science)

I raised our current pmix problem (Bug#1120424, #1120413)
upstream.

Ralph Castain upstream raises an interesting question,
https://github.com/openpmix/openpmix/issues/3717#issuecomment-3511548113

He suspect PRRTE might be at the heart of the problems we've got
running in buildd chroots with not internet interface (lo only).
His recommendation is to package PRRTE separately instead of using
the bundled source that comes with openmpi, just as we've started doing
with PMIx.

Would that work for us? Hard to say if it would make MPI packaging
harder or simpler, but might make it easier to backport upstream patches.

Cheers,
Drew