feat(crypto) Generate a cdylib for the crate.

Ask `rustc` to generate a dynamic system library, which will be useful
to generate a Wasm module.

crates/matrix-sdk-crypto/Cargo.toml

@@ -15,6 +15,9 @@ version = "0.4.1"
 features = ["docsrs"]
 rustdoc-args = ["--cfg", "docsrs"]
 
+[lib]
+crate-type = ["cdylib"]
+
 [features]
 default = []
 qrcode = ["matrix-qrcode"]

crates/matrix-sdk-crypto/src/lib.rs

@@ -15,8 +15,7 @@
 #![doc = include_str!("../README.md")]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![warn(missing_docs, missing_debug_implementations)]
-
-#[cfg(all(feature = "js", not(target_arch = "wasm32")))]
+#![cfg(all(feature = "js", not(target_arch = "wasm32")))]
 compile_error!(
     "The `js` feature must be enabled only for the `wasm32` target (either `wasm32-unknown-unknown` or `wasm32-wasi`)."
 );