Unfortunately that’s not possible. Architecturally, you really have to consider your Function folder to be truly standalone - that folder gets zipped into its own package then shipped off to AWS lambda where it will run on a machine somewhere with zero context of where it came from, that it’s tied to Netlify in any way, or what previous runs of the function did. A site’s static build and its functions are fully disconnected in terms of systems / machines / file structures / etc. – your functions are running fully stateless somewhere in the AWS cloud and your site files themselves are being served directly from Netlify’s Edge Network on CDN-like servers (geo-distributed). The two actually don’t know about each other at all. A Function cannot impact the site’s live files directly.
That said, there are some folks experimenting with Functions that commit to the underlying repository as a means of programmatically changing the site. GoTell is one such example - creating a comment system based on a repository containing a JSON file that a Function updates when a new comment comes in, commits the change, then a Netlify build kicks off. The transaction time is significantly slower than a normal web request (on the order of minutes // based on your build time rather than milliseconds), but it the use case works for you, it could be really useful.
I hope that helps! Happy to answer any followup questions