This seems like a rather hopeless endeavor…
When I finally got pkgs.runCommand to run it couldn’t find the source since it had no access to the home directory, nor the $src variable. The sources didn’t want to download with wget either (even if I included wget as a buildInput) because of a “failure in name resolution”.
It seems that “setting buildCommand overrides all the phases in a stdenv derivation.”: Using the `src` attribute in `runCommand`