re-add caching step

          saveRDS(remotes::dev_package_deps(dependencies = TRUE), "depends.Rds", version = 2)

        shell: Rscript {0}

      - name: Cache R packages

        if: runner.os != 'Windows'

        uses: actions/cache@v1

        with:

          path: ${{ env.R_LIBS_USER }}

          key: ${{ runner.os }}-r-${{ matrix.config.r }}-${{ hashFiles('depends.Rds') }}

          restore-keys: ${{ runner.os }}-r-${{ matrix.config.r }}-

      - name: Install system dependencies

        if: runner.os == 'Linux'

        env:

          RHUB_PLATFORM: linux-x86_64-ubuntu-gcc

        run: |

          Rscript -e "remotes::install_github('r-hub/sysreqs')"

          sysreqs=$(Rscript -e "cat(sysreqs::sysreq_commands('DESCRIPTION'))")

          sudo -s eval "$sysreqs"

      - name: Install dependencies

        run: |

          remotes::install_deps(dependencies = TRUE)