It would work the same way that it works for programs written in languages that aren't Rust. You're doing the classic thing where you're conflating a language with a given implementation.
The free software advocate's take: You say the toolchain from rust-lang.org makes this difficult? Granted—I'll take your word for it. Go fix that toolchain. (And as a side note, the fact that rust-lang.org chose LLVM is likely to do the opposite of cultivating sympathy.) It's a lot like the saying that goes something like, "poor planning on your end does not automatically make for an emergency on my end."
There’s a case to be made that Sequoia or another LGPL user should also invest in making it easier to comply with the LGPL with Rust tooling. But I doubt that will happen anytime soon.
The free software advocate's take: You say the toolchain from rust-lang.org makes this difficult? Granted—I'll take your word for it. Go fix that toolchain. (And as a side note, the fact that rust-lang.org chose LLVM is likely to do the opposite of cultivating sympathy.) It's a lot like the saying that goes something like, "poor planning on your end does not automatically make for an emergency on my end."