[PATCH] D42490: [cmake] Set cmake policy CMP0068 to suppress warnings on OSX

[Don Hinton via Phabricator via cfe-commits]

hintonda added a comment.

It turns out that policies don't survive a call to `cmake_minimum_required()`, so we need to rethink how llvm, et al, handles policies, e.g.:

- move `cmake_minimum_required()` inside the `if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )` branch.
- move all `cmake_policy()` commands from llvm/CMakeLists.txt into a separate file in llvm/cmake/modules and include that file in subordinate projects. below the `cmake_minimum_required()` command.


Repository:
  rC Clang

https://reviews.llvm.org/D42490