building libcxx in tree with cmake?

Are there any plans to enhance the build machinery in llvm 3.4 so that
the clang++ compiler can be built with libcxx support enabled by just
placing the libcxx sources in the projects directory like is done for
the compiler-rt support in llvm? Currently the cmake files don't seem
to support this option and libcxx has to be built and installed outside
of the llvm build tree. Thanks in advance for any clarifications.