`sccache` not being properly invalidated on changes to `.sol` files

Changes to `.sol` files are not properly invalidating the `sccache`. This is likely fixed by adding a `println!` to `build.rs` to ensure that we rebuild if any of the `.sol` files that are used change.

Example of a failing run:
https://github.com/risc0/risc0-ethereum/actions/runs/9037664809/job/24837174330