FreeBSD 10 ships with only libc++, make sure it's the default when compiling
c++ code.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194332 91177308-0d34-0410-b5e6-96231b3b80d8
Commit the changes to make libc++ the default on FreeBSD >= 10, rather than
just the test...



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194333 91177308-0d34-0410-b5e6-96231b3b80d8