Buildroot and Yocto are terrible build systems, let alone build systems for distros. Gentoo and its Portage are IMO really good for distro building, though I w

Buildroot and Yocto are terrible build systems, let alone build systems for distros. Gentoo and its Portage are IMO really good for distro building, though I would not say it is "small" or "simple". NixOS might also be a good distro builder, from the little I've read about it.