Add Clippy to the CI

ci/script.sh

@@ -5,6 +5,7 @@ set -ex
 # TODO This is the "test phase", tweak it as you see fit
 main() {
     cargo fmt --all -- --check
+    cargo clippy --all-targets --all-features -- -D warnings
     cross check --target $TARGET
     cross check --target $TARGET --release