fix(ffi): only build cdylib when the FFI cfg is active

Author: lqd

Cargo.toml

@@ -19,9 +19,6 @@ include = [
   #"build.rs",
 ]
 
-[lib]
-crate-type = ["lib", "staticlib", "cdylib"]
-
 [dependencies]
 bytes = "1"
 futures-core = { version = "0.3", default-features = false }

src/lib.rs

@@ -5,6 +5,11 @@
 #![cfg_attr(test, deny(warnings))]
 #![cfg_attr(all(test, feature = "nightly"), feature(test))]
 #![cfg_attr(docsrs, feature(doc_cfg))]
+#![cfg_attr(hyper_unstable_ffi, crate_type = "cdylib")]
+#![cfg_attr(
+    hyper_unstable_ffi,
+    allow(unknown_lints, deprecated_cfg_attr_crate_type_name)
+)]
 
 //! # hyper
 //!