build: make copy-node-modules.sh work

Two fixes:

* In the Dockerfile, add copy-node-modules.sh before `npm install`,
  since it is needed by the new postinstall hook.
* In paver/assets.py, run copy-node-modules.sh for backwards com-
  patibility, just for cases where `SKIP_NPM_INSTALL` is enabled
  (which would prevent our new postinstall hook from running
  automatically!). We will deprecate the paver asset commands all at
  once once the new non-paver stuff is 100% working.

Dockerfile

@@ -117,6 +117,7 @@ RUN pip install -r requirements/edx/base.txt
 
 # Install node and node modules
 RUN nodeenv /edx/app/edxapp/nodeenv --node=16.14.0 --prebuilt
+COPY scripts/copy-node-modules.sh scripts
 RUN npm install -g [email protected]
 COPY package.json package.json
 COPY package-lock.json package-lock.json

pavelib/assets.py

@@ -611,8 +611,7 @@ def process_npm_assets():
     """
     Process vendor libraries installed via NPM.
     """
-    print("\t\tProcessing NPM assets is now done automatically in an npm post-install hook.")
-    print("\t\tThis function is now a no-op.")
+    sh('scripts/copy-node-modules.sh')
 
 
 @task