SNAP_ORIGIN not been read from shell env

Testing ```site``` to deploy via CloudFlare Pages, does not read the ```SNAP_ORIGIN``` env from shell variables as per https://support.gatsbyjs.com/hc/en-us/articles/17278095696404-Environment-Variables-Specific-to-Gatsby-Cloud.

Tested locally with ```SNAP_ORIGIN=npm:testsnap yarn workspace site build --no-uglify``` and keeping getting the ```localhost:8080``` for the ```Connection request```.

Is this expected behaviour or am I missing something (quite possible) ... Hoping it's an oversight.

Start with the site workspace and run SNAP_ORIGIN=npm:testsnap yarn workspace site build --no-uglify, then trace how the build reads shell environment variables and produces the Connection request URL. Done means the build uses the supplied SNAP_ORIGIN instead of localhost:8080, with a test or documented verification for the behavior.

Written by the indexing model from the issue text.