[ci] upgrade R CI scripts to work on Ubuntu 20.04 (#4084)

* [ci] install additional LaTeX packages in R CI jobs

* update autoconf version

* bump upper limit on package size to 100

.ci/test_r_package.sh

@@ -18,7 +18,7 @@ export _R_CHECK_CRAN_INCOMING_REMOTE_=0
 # CRAN ignores the "installed size is too large" NOTE,
 # so our CI can too. Setting to a large value here just
 # to catch extreme problems
-export _R_CHECK_PKG_SIZES_THRESHOLD_=60
+export _R_CHECK_PKG_SIZES_THRESHOLD_=100
 
 # don't fail builds for long-running examples unless they're very long.
 # See https://github.com/microsoft/LightGBM/issues/4049#issuecomment-793412254.
@@ -59,6 +59,7 @@ if [[ $OS_NAME == "linux" ]]; then
             devscripts \
             r-base-dev=${R_LINUX_VERSION} \
             texinfo \
+            texlive-latex-extra \
             texlive-latex-recommended \
             texlive-fonts-recommended \
             texlive-fonts-extra \

.ci/test_r_package_windows.ps1

@@ -90,7 +90,7 @@ $env:_R_CHECK_CRAN_INCOMING_REMOTE_ = 0
 # CRAN ignores the "installed size is too large" NOTE,
 # so our CI can too. Setting to a large value here just
 # to catch extreme problems
-$env:_R_CHECK_PKG_SIZES_THRESHOLD_ = 60
+$env:_R_CHECK_PKG_SIZES_THRESHOLD_ = 100
 
 # don't fail builds for long-running examples unless they're very long.
 # See https://github.com/microsoft/LightGBM/issues/4049#issuecomment-793412254.

R-package/AUTOCONF_UBUNTU_VERSION

-2.69-11
+2.69-11.1

R-package/README.md

@@ -291,20 +291,20 @@ This section briefly explains the key files for building a CRAN package. To upda
 At build time, `configure` will be run and used to create a file `Makevars`, using `Makevars.in` as a template.
 
 1. Edit `configure.ac`.
-2. Create `configure` with `autoconf`. Do not edit it by hand. This file must be generated on Ubuntu 18.04.
+2. Create `configure` with `autoconf`. Do not edit it by hand. This file must be generated on Ubuntu 20.04.
 
-    If you have an Ubuntu 18.04 environment available, run the provided script from the root of the `LightGBM` repository.
+    If you have an Ubuntu 20.04 environment available, run the provided script from the root of the `LightGBM` repository.
 
     ```shell
     ./R-package/recreate-configure.sh
     ```
 
-    If you do not have easy access to an Ubuntu 18.04 environment, the `configure` script can be generated using Docker by running the code below from the root of this repo.
+    If you do not have easy access to an Ubuntu 20.04 environment, the `configure` script can be generated using Docker by running the code below from the root of this repo.
 
     ```shell
     docker run \
         -v $(pwd):/opt/LightGBM \
-        -t ubuntu:18.04 \
+        -t ubuntu:20.04 \
         /bin/bash -c "cd /opt/LightGBM && ./R-package/recreate-configure.sh"
     ```
 

R-package/recreate-configure.sh

 #!/bin/bash
 
 # recreates 'configure' from 'configure.ac'
-# this script should run on Ubuntu 18.04
+# this script should run on Ubuntu 20.04
 AUTOCONF_VERSION=$(cat R-package/AUTOCONF_UBUNTU_VERSION)
 
 # R packages cannot have versions like 3.0.0rc1, but