Installation of R packages with install.R fails

[rgaiacs]

This is a regression introduced in #1432.

R --vanilla disable the execution of Rprofile.site and .Rprofile. This means that the Rprofile.site created in

#7 [18/32] RUN R RHOME && mkdir -p /etc/rstudio && EXPANDED_CRAN_MIRROR_URL="$(. /etc/os-release && echo https://packagemanager.posit.co/all/__linux__/${VERSION_CODENAME}/2025-07-01+OM7RXCua | envsubst)" && echo "options(repos = c(CRAN = "${EXPANDED_CRAN_MIRROR_URL}"))" > /opt/R/4.4.2/lib/R/etc/Rprofile.site && echo "r-cran-repos=${EXPANDED_CRAN_MIRROR_URL}" > /etc/rstudio/rsession.conf

is not executed and a call of install.packages() results in

Error in contrib.url(repos, type) : 
  trying to use CRAN without setting a mirror
Calls: install.packages -> startsWith -> contrib.url

The --vanilla should be replaced with

--no-save --no-restore --no-init-file --no-environ