Suppress static file creation in gatsby-source-filesystem?

[mwfrost]

I've encountered a situation where I'd like to use gatsby-source-filesystem to traverse a directory and create GraphQL nodes for each file, but I don't want to copy them to the static folder. It would be great to have a createStaticFile flag that I could turn off, and thereby bypass the step in extend-file-node.js that copies the file to the static directory.