> This splits our native cctools package into two additional packages: native_clang and native_libtapi. This is in an effort to not only make our mac toolchain more understandable, but also to reduce duplication.
>
> Everything about the current build process should remain the same. For gitian, that is:
>
> - Download LLVM Clang 8.0.0 binary.
> - Build libtapi using downloaded Clang.
> - Build cctools using downloaded Clang and libtapi.
> - Build the rest of depends..
>
> For Guix (FORCE_USE_SYSTEM_CLANG=1):
>
> - Build libtapi using using system Clang.
> - Build cctools using system Clang and libtapi.
> - Build the rest of depends..
This is a backport of core#21457