On incremental builds' reproducibility about toybox HOT 1 OPEN

I've een working on reproducible build stuff for 20 years (https://landley.net/aboriginal/about.html and https://lists.j-core.org/pipermail/j-core/2016-August/000314.html and so on) but "we changed the config and did an incremental build" is not a use case I've particularly been targeting.

The top level makefile is mostly just a wrapper, the build is done by scripts/make.sh which should reuse artifacts (ala generated/obj/*.o). You can set V=1 to see what the build is doing (same as the kernel build). The "distclean" target deletes .config, you probably want the "clean" target (again, same as the kernel build).

The build checks which commands need to be rebuilt, but the toybox global symbols (CONFIG_TOYBOX_*) are not checked, and can theoretically vary if you don't do a clean build. The reason I don't check if they changed is I don't (reliably) have a copy of the previous build's .config to compare it with, and considered doing that "pilot error".

The 0.8.5 release was 3 years ago, I don't remember specifically what's changed since then. (Rather a lot, including a significant chunk of the build plumbing. I note that the https://github.com/landley/toybox/blob/master/scripts/recreate-prereq.sh and https://github.com/landley/toybox/tree/master/scripts/prereq work was fairly recent, ala http://lists.landley.net/pipermail/toybox-landley.net/2024-April/030271.html)

from toybox.