hexo_: putting it in /nix seems a little sketchy. i think you would be better off just doing:

```
{
  busybox = builtins.fetchurl "https://hydra.nixos.org/job/nixpkgs/cross-trunk/bootstrapTools.powerpc64le.dist/latest/download/1//busybox";
  bootstrapTools = builtins.fetchurl "https://hydra.nixos.org/job/nixpkgs/cross-trunk/bootstrapTools.powerpc64le.dist/latest/download/1/bootstrap-tools.tar.xz";
}
```