In Chapter 9.1 of the book, it says:
If you’re in a situation where you need to make the resulting binary as small as possible, you can switch from unwinding on panic to aborting on panic by adding panic = ‘abort’ to the appropriate [profile] sections in your Cargo.toml.
When I add that to my Cargo.toml, and run
cargo build, I get:
warning: unused manifest key: profile.panic
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs