PGI Fortran: link failure with Mac OS X

[hppritcha]

@PHHargrove 's testing of the 2.0.2rc1 with PGI 16.10 compiler showed issues with symbol relocation problems for code generated with PGI's fortran compiler:

https://mail-archive.com/devel@lists.open-mpi.org/msg19823.html

[PHHargrove]

Retest w/ Open MPI 3.0.0rc1 and PGI-17.4 shows that nothing has changed.

[hppritcha]

@sjeaugey we need to know whether or not Nvidia will be supporting PGI on OS-x. If not, then we will indicate in the README that we don't support PGI on OS-x for Open MPI.

[hppritcha]

@gvallee here's on of the PGI related issues

[gvallee]

No news from PGI yet but we are trying to reach them again.

[gvallee]

PGI said it has been forwarded to the appropriate developer but did not give a timeframe for a potential fix.

[hppritcha]

not going to address in 2.0.4.