Reason I'm asking about ENV vars is because what you're doing above with `DEBIAN_FRONTEND` suggests that this could just be the following:

```
ENV NODE_VERSION v0.10.22
RUN curl -s http://nodejs.org/dist/$NODE_VERSION/node-$NODE_VERSION-linux-x64.tar.gz | tar xzf - --strip-components=1
```

That way you could get rid of the `Dockerfile.in`, the `NODE_VERSION` file, and the extra `make` targets.