In the default `fixupPhase` the output of `substituteAllStream` is
streamed to setup-hook.
`stdenv.cc.bintools.overrideAttrs { NIX_DEBUG = 6; }`
With `NIX_DEBUG` contains:
```
@expandResponseParams@ -> /nix/store/yl01rd58vp4m8bbhkihpk132cprfmx6f-expand-response-params/bin/expand-response-params
...
```