Using the new C++11 stack on 9.1

[Marcus Karlsson]

Hello.

I was very happy when I received the 9.1 announcement in my mailbox,
especially when I read about the inclusion of the new C++11 stack
including LLVM libc++ and libcxxrt. So I decided to test it on a 9.1
system:

    clang++ foo.cc -stdlib=libc++

However, the compilation fails:

    /usr/bin/ld: cannot find -lc++

It's available in the source tree for 9.1, my assumption is that it's
just not installed by default.

What should I do in order to use it? I have not found much documentation
on it other than it will be the default in 10.

Marcus