That's not the problem. The real problem is that if I convince you to run my script, it's going to be quite easy to convince you to give me extra permissions, so I can get to your data. It really irks me when things like Cargo are doing exactly that, make me run a sh script. Cargo and the likes, are making running sh scripts way too common.
I assume you mean rustup, not cargo specifically or am I wrong?
cargo builds/runs build.rs in the background
Yeah, that was a brain fart.