cmake CMAKE_SYSTEM_INCLUDE_PATH examples

Lewuathe/mlir-hello thirdparty/llvm-project/libunwind/src/CMakeLists.txt :122 

find_path(LIBUNWIND_HAIKU_PRIVATE_HEADERS
            "commpage_defs.h"
            PATHS ${CMAKE_SYSTEM_INCLUDE_PATH}
            PATH_SUFFIXES "/private/system"
            NO_DEFAULT_PATH
            REQUIRED)