[MacPorts] #44129: cmake: fix build against libc++ on Lion

[MacPorts]

#44129: cmake: fix build against libc++ on Lion
----------------------+-------------------
  Reporter:  mojca@…  |      Owner:  css@…
      Type:  defect   |     Status:  new
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:  lion
      Port:  cmake    |
----------------------+-------------------

Comment (by mojca@…):

 The compile is even more broken than what I though:
   * http://www.cmake.org/Bug/view.php?id=15039#c36490

 Anyway, if we would start "officially supporting" `libc++` for the sake of
 better support for C++11, I would suggest to pick clang-3.4 as the default
 compiler (if that is feasible).

-- 
Ticket URL: <https://trac.macports.org/ticket/44129#comment:8>
MacPorts <http://www.macports.org/>
Ports system for OS X