Add comments on crate-type switch

Cargo.toml

@@ -7,6 +7,10 @@ edition = "2021"
 crate-type = ["cdylib"]
 
 [[example]]
+# crate-type can't be (at the moment) be overriden for specific targets
+# src/wasm_lib.rs forwards to src/lib.rs so that we can change from cdylib
+# (that is needed while compiling natively) to staticlib (needed since the
+# actual linking will be done via emcc
 name = "rusty_quack"
 path = "src/wasm_lib.rs"
 crate-type = ["staticlib"]

src/wasm_lib.rs

@@ -1,3 +1,14 @@
 #![allow(special_module_name)]
 
 mod lib;
+
+// To build the Wasm target, a `staticlib` crate-type is required
+//
+// This is different than the default needed in native, and there is
+// currently no way to select crate-type depending on target.
+//
+// This file sole purpose is remapping the content of lib as an
+// example, do not change the content of the file.
+//
+// To build the Wasm target explicitly, use:
+//   cargo build --example $PACKAGE_NAME