See libfuzzer-sys.
It uses cargo-fuzz, which requires a special directory structure.
This directory (the Cargo.toml and src/lib.rs) are just empty placeholders to make cargo-fuzz happy.
The real folder of interest is fuzz/, especially Cargo.toml and fuzz_target.rs there.
Run the fuzzer with something like cargo +nightly fuzz run fuzz_target -- -max_total_time=1800.