Adding MPI back to Boost

[Ryan Schmidt]

On Dec 14, 2014, at 2:28 AM, Sean Farley wrote:

> So, I've added support into the compilers portgroup for working with
> the compiler.blacklist variable but that doesn't fix the issue that Ryan
> tried to fix with r125939:
> 
> https://trac.macports.org/changeset/125939
> 
> It seems instead that the fix is just to remove the gcc variants:
> 
> mpi.setup -gcc
> 
> Is there anything wrong with this proposed fix? If no one objects, I'll
> push my changesets which 1) add blacklist support to the compilers
> portgroup and 2) add mpi portgroup to boost (but remove gcc variants).

Right, using gcc variants causes the use of libstdc++ which causes the problem on Mavericks and later.

So, without gcc variants, what variants remain?