🔧(docker) set variable env used by vite to build standalone site

In order to build correctly the stansalone site with vite, we have to
set the environment variable VITE_DIR_PROD and VITE_CDN_REPLACE_KEYWORD

Dockerfile

@@ -54,7 +54,7 @@ COPY ./src/.prettierrc.js /app/
 RUN yarn compile-translations && \
     yarn workspace marsha run sass scss/_main.scss /app/marsha/static/css/main.css --style=compressed --load-path=../../node_modules  && \
     mkdir -p /app/marsha/static/css/fonts && cp node_modules/katex/dist/fonts/* /app/marsha/static/css/fonts && \
-    BUILD_PATH=/app/marsha/static/js/build/site/ DJANGO_STATIC_DIR=/app/marsha/static yarn workspace standalone_site run build && \
+    VITE_DIR_PROD=/app/marsha/static/js/build/site/ VITE_CDN_REPLACE_KEYWORD=/__static_base_url__/ yarn workspace standalone_site run build && \
     yarn workspace marsha run build --mode=production --output-path /app/marsha/static/js/build/lti_site/
 
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