fix: Write webpack stats file to right place (so static assets can load)

After the removal of paver, static assets build wasn't completing properly
in edxapp -- static files were written to the correct directory in the
assets volume (mounted under /edx/var) but the webpack-stats.json files
were written to the test_root dir in the app container (under /edx/app).
The service would fail on first page load as it failed to find the stats
file, which is apparently used for locating resources.

The static assets build was also taking quite a long time and a lot of CPU,
which is likely because we were doing the production-style build with full
optimization.

- Set static-root environment variables so that webpack-stats.json is
  written to the right place. See `staticRootLms` and `staticRootCms` in
  `webpack.common.config.js` in edx-platform for where that default is set.
  Set both LMS/CMS vars for both lms and cms since there's some dependency
  of CMS on LMS in the logic (and both calls build both sets of files, for
  better or worse).
- Use npm dev build for reduced optimization (faster build).

Also:

- Use same spelling of `--no-input` for both calls (either works, just
  make it uniform)

Addresses #65

Makefile

@@ -443,11 +443,14 @@ $(foreach asset_service,$(ASSET_SERVICES_LIST),\
 
 dev.static: | $(_asset_compilation_targets)
 
+# Put webpack-stats.json in the right place during NPM build:
+EDXAPP_STATIC_ROOT_ENV=STATIC_ROOT_LMS=/edx/var/edxapp/staticfiles STATIC_ROOT_CMS=/edx/var/edxapp/staticfiles/studio
+
 dev.static.lms:
-	docker compose exec -T lms bash -c 'source /edx/app/edxapp/edxapp_env && cd /edx/app/edxapp/edx-platform/ && npm run build && ./manage.py lms collectstatic --noinput'
+	docker compose exec -T lms bash -c "source /edx/app/edxapp/edxapp_env && cd /edx/app/edxapp/edx-platform/ && $(EDXAPP_STATIC_ROOT_ENV) npm run build-dev && ./manage.py lms collectstatic --no-input"
 
 dev.static.cms:
-	docker compose exec -T cms bash -c 'source /edx/app/edxapp/edxapp_env && cd /edx/app/edxapp/edx-platform/ && npm run build && ./manage.py cms collectstatic --no-input'
+	docker compose exec -T cms bash -c "source /edx/app/edxapp/edxapp_env && cd /edx/app/edxapp/edx-platform/ && $(EDXAPP_STATIC_ROOT_ENV) npm run build-dev && ./manage.py cms collectstatic --no-input"
 
 dev.static.%: ## Rebuild static assets for the specified service's container.
 	docker compose exec -T $* bash -c 'source /edx/app/$*/$*_env && cd /edx/app/$*/$*/ && make static'