>it is mostly your build-systems' job to be hermetic, run anywhere, handle cross-builds etc.

yes, and... the idea here is that it would be neat to extend the hermetic builds idea such that this can be run locally / anywhere where there's compute easily. The root problem that's being called out here is that idea of running something until the CI says it's green when there's a change, commit, network call, in the cycle is a pain in the ass. (The best way to avoid this churncycle is to just never write bugs! TFIC ;P)