CMake Policy CMP0042 and MACOSX_RPATH setting for libc++ and libc++abi

Hi All,

I'm a bit out of my depth on this one. I want to silence the CMake
warnings about MACOSX_RPATH.
I've read quite a bit about rpath and its handling on OSX but I still
don't fully understand it.

documentation for the MACOSX_RPATH CMake option can be found here:
http://www.cmake.org/cmake/help/v3.0/prop_tgt/MACOSX_RPATH.html

Would anybody be able to offer some advice on how to handle this?
Are there any issues with adopting this policy CMP0042 and enabling
MACOSX_RPATH by default?

/Eric