[wizzwizz4]

Just because you can do something, doesn't mean you should. A `build.rs` is supposed to be for compiling non-Rust code and stuff like that, not mucking about with the package manager – and by and large, people don't use it for mucking about with the package manager.

[pjmlp]

People use it to muck with the host OS in any possible way, unless one bothers to do the necessary code audit.

Besides that was just one example, there are plenty of them with turing complete languages.