Only FreeBSD 10-Current supports libc++?

I believe you are talking about libc++ which is a part of LLVM project. AFAIK it is not complete yet and by the time FreeBSD 9 was released the situation was even worse. You may try to follow build instructions on their website.
 
Those build instructions don't work. I hope that libc++ will be added to the 9-STABLE branch soon.
 
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