Dev not available to integrate a pull request and start a build? Download the appropriate build arch image, fire up VirtualBox, sync the repo (and apply a pull request if the dev hasn't had a chance to do that yet) and start the build script.
This doesn't entirely solve the problem, if nobody has submitted a fix yet, and you don't know enough to pull in the upstream fix and merge it yourself, you're at the mercy of some other user having that knowledge and making a pull request. It does close the gap somewhat though.
Are there existing projects to help get to this level of build reproducibility that can serve as a base to use? It would be awesome to know people are already working on making this easy to adopt.
The problem is that it is a giant codebase, you need to compile C++, Rust for hours. Even pulling the latest code is an ordeal.
It's not feasible on lowly workstations and garden variety cheap cloud VM builders, the performance is just crap.