add empty library directory

testing/get-renv.ps1

@@ -0,0 +1,7 @@
+$dir = "C:\R\R-win.exe"
+$urlR = "https://cran.r-project.org/bin/windows/base/R-4.0.3-win.exe"
+$outputR = "$dir\R-win.exe"
+$wcR = New-Object System.Net.WebClient
+$wcR.DownloadFile($urlR, $outputR)
+$dirR = $dir + "R-win.exe"
+Start-Process -FilePath $dirR -ArgumentList "/S /v/qn"

testing/get-renv.sh

@@ -1,2 +1,9 @@
 #!/usr/bin/env bash
 sudo apt install r-base
+# create empty folder for user library.
+# necessary for non-root users who have
+# never installed an R package before.
+# Alternatively, we require the renv
+# package to be installed already, then we can
+# omit that.
+Rscript -e 'dir.create(Sys.getenv("R_LIBS_USER"), recursive = TRUE)'