Free/NetBSD: PMIX build failures using OpenMPI 2.1.0rc2

[hppritcha]

@PHHargrove reported a PMIX build failure when trying to build OpenMPI 2.1.0rc2 for Free/NetBSD systems at his disposal:

https://www.mail-archive.com/devel@lists.open-mpi.org//msg19986.html

He's providing a patch.

[rhc54]

Fixed here: openpmix/openpmix#326

Will patch OMPI shortly

[hppritcha]

Closed via #3118