PGI: libevent build failure on Mac OS-x

[hppritcha]

libevent has a configury problem that prevents building the OMPI internal version of libevent
on OS-X when using PGI compilers (including 16.10).

The problem is described in more detail in this posting to devel:

https://mail-archive.com/devel@lists.open-mpi.org/msg19824.html

[hppritcha]

@sjeaugey any updates for this issue?

[sjeaugey]

I'm not sure what we should do on our side. Reading Paul's email, it seems someone added this GCC-specific flag which broke compilation with PGI on darwin. Should we remove it ? Or only add this flag when the compiler is GCC ?

[jsquyres]

@sjeaugey Agreed -- it seems like libevent's configury is incorrectly adding that compiler flag. It seems like it would be a relatively straightforward configury fix (although for best results, it should probably also be sent upstream to libevent). Can you supply a PR?

[hppritcha]

Another case of updating the README to indicate that we don't support PGI on OS-x.

[hppritcha]

@gvallee and here's another one.

[hppritcha]

closing.