This option is problematic, and has never worked in an Open MPI v4.0.x
release tarball. Given that PMIx is now available elsewhere, it isn't
worth fixing this option.
See https://github.com/open-mpi/ompi/issues/6228 for more detail.
NOTE: This is a v4.0.x-specific commit because this option no longer
exists on master because we deleted the entire pmix3x component.
Hence, it's not possible to cherry-pick anything from master back to
the v4.0.x branch.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
(cherry picked from commit 447b14061880e218371f9eb0cbe427b8358d45b8)