Try again to get nix+crane+rust+wasm working.

flake.nix

@@ -8,19 +8,32 @@
     };
 
     flake-utils.url = "github:numtide/flake-utils";
+
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-utils.follows = "flake-utils";
+      };
+    };
   };
 
-  outputs = { self, nixpkgs, crane, flake-utils, ... }:
+  outputs = { self, nixpkgs, crane, flake-utils, rust-overlay, ... }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs {
           inherit system;
+          overlays = [ (import rust-overlay) ];
         };
 
         rustToolchain = pkgs.rust-bin.stable.latest.default.override {
           targets = [ "wasm32-unknown-unknown" ];
         };
-        craneLib = crane.lib.${system};
+        craneLib = ((crane.mkLib pkgs).overrideToolchain rustToolchain).overrideScope' (_final: _prev: {
+          # The version of wasm-bindgen-cli needs to match the version in Cargo.lock. You
+          # can unpin this if your nixpkgs commit contains the appropriate wasm-bindgen-cli version
+#          inherit (import nixpkgs-for-wasm-bindgen { inherit system; }) wasm-bindgen-cli;
+        });
         all = craneLib.buildPackage {
           # NOTE: we need to force lld otherwise rust-lld is not found for wasm32 target
           CARGO_TARGET_WASM32_UNKNOWN_UNKNOWN_LINKER = "lld";