One way of maybe getting that target set would be to locate the targets for files in the patch set, list dependencies of those targets, for targets in that list, see which source files are missing, identify those targets as targets needed to run to generate files needed for the patch set.

An alternative approach would be to just generate all files, every time if not too expensive, or so something more clever where generated files are shared between patch sets where possible. This second alternative is appealing for its simplicity, provided that is it not too costly. But, there would need to be a way to generate all files in one run and this includes building of generators.

We have started to experiment with a full "non-build", except for building of generators needed for the build itself.