You can set the name of the static folder to use in your configuration file, for example config.toml. From Hugo 0.31 you can configure as many static directories as you need. All the files in all the static directories will form a union filesystem.
The English site will get its static files as a union of “static1”, “static2” and “static_en”. On file duplicates, the right-most version will win.
The Norwegian site will get its static files as a union of “staticDir_override” and “static_no”.
Note: The 2static2 (can be a number between 0 and 10) is added to tell Hugo that you want to add this directory to the global set of static directories. Using staticDir on the language level would replace the global value.
Note: The example above is a multihost setup. In a regular setup, all the static directories will be available to all sites.