Building the toolchain on nixos

Dear Genodians,

Has anyone already built the toolchain for nixos? and happens to have a `flake.nix` or a `.nix` source file that can build it, I think those are called 'derivation'.

I am currently down that rabbit hole, and have the following error:

``` $ ./tool/tool_chain x86 <...> The directory (BUILD_SYSTEM_HEADER_DIR) that should contain system headers does not exist:     /usr/include ```

I haven't modified the `tool/tool_chain` tool or patched configure to adjusted standard paths, to point to their respective 'stores' yet. I only have adjusted the shebangs to `#!/usr/bin/env -S ...` where needed.

Cheers, alice