Everything is getting recompiled all the time anyway. At least with FreeBSD, any time a dependency is updated, all the packages that depend on that package get rebuilt. There's no concept of "this was a small update and its dynamically linked", its just "the version string changed, so rebuild everything that lists it as a dependency". This is particularly "fun" for web browsers because they have a lot of dependencies, ensuring they're rebuilt often, and they take a long time to build.