[PATCH] Fix libc++ header install on darwin.

[Justin Bogner]

Jean-Daniel Dupas <devlists at shadowlab.org> writes:
> On darwin, clang looks for libc++ headers in 'lib/c++/v1' and not in
> 'include/c++/v1' like on other OSes.
> 
> This patch update the libc++ CMake build system to install the libc++
> headers at the right place on darwin.

I discussed this with a few people and the general consensus seems to be
that the other direction makes more sense, ie, we should expect the
headers in include/.

I sent a patch to that effect, which should obsolete this one as long as
no one is opposed to it.