Commit 1795495ad3f6 introduced a novolume/Dockerfile to build an image without extra volumes.

@Kaliiixx has noticed it doesn't build on Docker Hub servers:

Build failed: Forbidden path outside the build context: ../files ()

Each root folder, ie a folder where a Dockerfile is present, must have the full context, ie here the all the folder files/.

Symbolic links aren't warranted to be well supported.

We so need to provide a files/ folder for the novolume/ directory, and sync it with the main files folder.