[Bug]: Gatsby Functions is skipped even if they exists

[sjelfull]

Summary
I have a vanilla install of Gatsby + one Gatsby function. I installed to support Gatsby on Netlify.

Before upgrading to the newest version of gatsby-plugin-netlify it would detect functions as expected.

After upgrading, it skips building Gatsby functions.

Steps to reproduce

1. Pull down reproduction repro-gatsby-netlify-functions-plugin
2. Deploy to Netlify
3. See message Skipping Gatsby Functions and SSR/DSG support because gatsby-plugin-netlify reported that this site does not use them.

Plugin version
5.0.0

[orinokai]

Closing as dup of netlify/netlify-plugin-gatsby#385