It’s all in the article.
But this isn't a Rust developer issue so much as a distro and security issue. Most Rust developers don't have to concern themselves with supply chain attacks or security audibility, so to them this probably seems like a weird thing to focus on.
But as someone who does have to worry about such things, trading off the ability to audit your supply chain for a small, one-time compilation boost on your first compile is a _terrible_ trade-off.