Fix for windows installation tensorflow#7341

Fix a problem with the installation on windows.
My problem on windows was that `./lib/napi-v9` directory didn't exist and `./scripts/deps-stage.js` on line **60** needed the path to symlink or copy the dll. 

My fix was to make sure that the directory `napi-v9` exists with:
`await fs.mkdir(path.dirname(destLibTensorFlowPath), {recursive: true})`;

I'm solving the copy issue with this code.

tfjs-node/scripts/deps-stage.js

@@ -57,6 +57,7 @@ async function symlinkDepsLib() {
     throw new Error('Destination path not supplied!');
   }
   try {
+    await fs.mkdir(path.dirname(destLibTensorFlowPath), {recursive: true});
     await symlink(
         path.relative(
             path.dirname(destLibTensorFlowPath), depsLibTensorFlowPath),