libcxxabi was having issues with detecting flags in config-ix.cmakecorrectly when cross compiling.
I narrowed it down to changes as a result of including
list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}") include("${LLVM_CMAKE_PATH}/AddLLVM.cmake") include("${LLVM_CMAKE_PATH}/HandleLLVMOptions.cmake")
The best way to solve this was to rework CMake to use modules to mirror libcxx.
This makes the cmake source more readable and maintainable