install xz in images by default

docker/Dockerfile-alpine-320

@@ -16,7 +16,7 @@ ARG GITHUB_PAT
 # Background: JAGS needs lapack & lapack-dev but these conflict with openblas-dev which is required by R-dev
 # Solution: first compile JAGS, then remove lapack & lapack-dev again
 # # xvfb: for graphical pkgs requiring tcl, like gWidgets2tcltk
-RUN apk add -q --no-cache curl tar make lapack lapack-dev blas blas-dev gcc gfortran g++ htop git cmake tk-dev xvfb xvfb-run
+RUN apk add -q --no-cache curl tar make lapack lapack-dev blas blas-dev gcc gfortran g++ htop git cmake tk-dev xvfb xvfb-run xz
 
 ### CUSTOM DEPENDENCIES 
 # These usually are not packaged in OS repositories and need to be installed from source
@@ -50,7 +50,7 @@ RUN R -q -e 'install.packages("remotes", repo = "cloud.r-project.org"); remotes:
 # deps from pak::pkg_deps(".")$package
 RUN R -q -e 'pak::pak(c("DBI", "R6", "RPostgres", "Rcpp", "askpass", "base64enc", "bit64", "bit", "blob", "callr", "cli", "credentials", "curl", "data.table", "desc", "digest", "dplyr", "fansi", "fs", "future.apply", "future", "generics", "gert", "globals", "glue", "hms", "httr", "jsonlite", "lgr", "lifecycle", "listenv", "lubridate", "magrittr", "mime", "openssl", "parallelly", "paws.common", "paws.storage", "pillar", "pkgbuild", "pkgconfig", "processx", "progressr", "ps", "purrr", "rlang", "rstudioapi", "s3fs", "stringi", "stringr", "sys", "tibble", "tidyselect", "timechange", "utf8", "vctrs", "withr", "xml2", "zip", "codetools", "cranlike", "RSQLite", "cachem", "crayon", "debugme", "fastmap", "memoise", "progress"))'
 
-COPY . .
+COPY --link . .
 # remove secrets from COPY
 RUN touch /.Renviron /.envrc && rm /.Renviron /.envrc
 RUN R CMD INSTALL . && rm -rf r-pkg-binaries