nix: build with parallelism feature

- explicitly disable features in the rust-ts wasm build - we don't have
CUDA support there

Author: arilotter

nix/lib.nix

@@ -57,7 +57,7 @@ let
   rustWorkspaceArgs = rustWorkspaceDeps // {
     inherit env src;
     strictDeps = true;
-    cargoExtraArgs = "--features python-extension";
+    cargoExtraArgs = "--features python-extension,parallelism";
   };
 
   rustWorkspaceArgsWithPython = rustWorkspaceArgs // {
@@ -100,7 +100,7 @@ let
     craneLib.buildPackage (
       rustWorkspaceArgs
       // {
-        inherit cargoArtifacts;
+        cargoExtraArgs = ""; # *remove* features - we don't want the cuda stuff in here.
         pname = name;
         doCheck = false;