[Linux] Provide support for prerm script for Debian package

In the context of SceneBuilder I'd like to move one level up some files that the packager put in the app dir once wrapped into the Debian package.
I can easily do a move of them into a postinst script that is supported by the FX packager but problem is that at uninstall time I must implement the symmetric file removal into a prerm script for which no support is provided.Without such a support a file moved in a postinst script will remain on disk once the product is uninstalled.