Add a c_bindings test to check-compiles.sh as it should build

Author: TheBlueMatt

ci/check-compiles.sh

@@ -7,3 +7,4 @@ cargo doc
 cargo doc --document-private-items
 cd fuzz && RUSTFLAGS="--cfg=fuzzing" cargo check --features=stdin_fuzz
 cd ../lightning && cargo check --no-default-features --features=no-std
+cd .. && RUSTC_BOOTSTRAP=1 RUSTFLAGS="--cfg=c_bindings" cargo check -Z avoid-dev-deps