new OS dep required by pkgdown (#4718)

Author: jangorecki

.gitlab-ci.yml

@@ -301,7 +301,7 @@ integration: ## merging all artifacts to produce single R repository, documentat
     R_DEVEL_BIN_VERSION: "4.1"
   script:
     ## pkgdown installs pkgs from "." so run at start to have clean root dir
-    - apt-get update -qq && apt-get install -y libxml2-dev
+    - apt-get update -qq && apt-get install -y libxml2-dev libfontconfig1-dev ## fontconfig1 for #4717
     - mkdir -p /tmp/pkgdown/library
     - R_LIBS_USER=/tmp/pkgdown/library Rscript -e 'install.packages("pkgdown", repos=Sys.getenv("CRAN_MIRROR"), quiet=TRUE); pkgdown::build_site(override=list(destination="./pkgdown"))'
     ## html manual, vignettes, repos, cran_web, cran_checks