Installs qpdf package for CRAN check in GitHub Actions

Author: HyukjinKwon

.github/workflows/master.yml

@@ -164,7 +164,8 @@ jobs:
     - name: Install R packages
       if: contains(matrix.modules, 'sparkr')
       run: |
-        sudo apt-get install -y libcurl4-openssl-dev
+        # qpdf is required to reduce the size of PDFs to make CRAN check pass. See SPARK-32497.
+        sudo apt-get install -y libcurl4-openssl-dev qpdf
         sudo Rscript -e "install.packages(c('knitr', 'rmarkdown', 'testthat', 'devtools', 'e1071', 'survival', 'arrow', 'roxygen2'), repos='https://cloud.r-project.org/')"
         # Show installed packages in R.
         sudo Rscript -e 'pkg_list <- as.data.frame(installed.packages()[, c(1,3:4)]); pkg_list[is.na(pkg_list$Priority), 1:2, drop = FALSE]'