Easiest option is to just add a tween or NewResponse subscriber to your app that handles responses from that url prefix.
If you don't like hard-coding the url prefix, then another option is to use a route factory on the static view which can annotate the request. You can then use this info in a tween or NewResponse subscriber to determine whether to set the header. I have a gist of this method here
https://gist.github.com/mmerickel/d9efb2ab358be75e6767 which you may find useful.
In the future I'd like to make the static view more extensible in this regard. In 1.8 we are considering adding support for view derivers that know about static views, so they can wrap them exclusively. You could then define a view deriver for static views which could affect only their responses with no performance impact on other views.
There are a couple other tickets open with respect to wrapping the static view response as well.