[main]: fix cache

Dockerfile

@@ -27,7 +27,7 @@ COPY .Rprofile /srv/shiny-server/.Rprofile
 # Prevent renv attempting to use pak
 ENV RENV_CONFIG_PAK_ENABLED=FALSE
 ENV RENV_DOWNLOAD_METHOD=libcurl
-ENV RENV_PATHS_CACHE=/opt/renv/cache
+ENV RENV_PATHS_CACHE=/srv/shiny-server/renv/cache
 
 # Some CRAN packages in this lockfile fail under Ubuntu hardening defaults
 # because -Werror=format-security turns benign warnings into build failures.
@@ -38,9 +38,7 @@ RUN for f in /usr/local/lib/R/etc/Makeconf /usr/lib/R/etc/Makeconf; do \
     done
 
 # Install renv and restore project packages
-RUN --mount=type=cache,target=/opt/renv/cache \
-    --mount=type=cache,target=/root/.cache/R/renv \
-    R --vanilla -e "install.packages('renv', repos='https://cran.rstudio.com')" && \
+RUN R --vanilla -e "install.packages('renv', repos='https://cran.rstudio.com')" && \
     R --vanilla -e "source('.Rprofile'); renv::restore(prompt=FALSE)"
 
 # Copy the application after dependencies so regular code changes do not