cmake build of lldb was complaining about missing files.

Example:
CMake Error at cmake/modules/LLVMProcessSources.cmake:89 (message):
  Found unknown source file
  /llvm-toolchain-3.3~svn179293.cmake/tools/lldb/source/Plugins/Platform/MacOSX/PlatformDarwinKernel.cpp



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@179295 91177308-0d34-0410-b5e6-96231b3b80d8