So I’m not saying this would actually be useful ( maybe it is ) but based on the description of a derivation as “a single build step”, could someone split a build into individual cc -c FILE definitions as well as linker invocations?
Despite being incredibly slow, I think if attributes expressed compilation flags you could limit nix build runs to only recompile changed targets.
While individual files are likely too fine grained to be practical, I do think there could be a value in subdivided packages for things like VBox ( maybe on the scale of individual binaries ).
The idea of using tools like bear or libtool to scrape builds to generate these has crossed my mind.