We have actually some files which are created during the build process. More temporary files are coming and we should place them all in the same tmp/ directory and not spreading them around :)
Examples for files actually in use could be:
In fact there is 2 needs: - temporary files needed at build time (like cache) - static files generated at build time needed later
The first would fit nice in tmp, while the later would fit in out/static/.. I did the second in fpo for the cloud selector (#132).
We are slowly moving all sites to a new layout, better not to create shared directories actually. Let's reopen this (if we still want to have it) after all websites moved to the new layout.