Include PCRE2 in R 3.x on Debian 11 for Pango support

In Debian 11, Pango now depends on PCRE2, so R 3.x will not be compiled with
Pango support if we hide PCRE2 to prevent R 3.5 and 3.6 from taking an unnecessary
dependency on PCRE2.

To check if R 3.x was compiled without Pango support, look for this line in the
configure output:

checking whether pkg-config knows about cairo and pango... no

Or in R, check if the "bitmapType" option defaults to "Xlib" instead of "Cairo":

> getOption("bitmapType")
"Xlib"

builder/Dockerfile.debian-11

@@ -19,6 +19,9 @@ RUN gem install fpm
 # Override the default pager used by R
 ENV PAGER /usr/bin/pager
 
+# R 3.x requires PCRE2 for Pango support on Debian 11
+ENV INCLUDE_PCRE2_IN_R_3 yes
+
 COPY package.debian-11 /package.sh
 COPY build.sh .
 ENTRYPOINT ./build.sh

builder/build.sh

@@ -70,7 +70,12 @@ compile_r() {
   # Since there's no way to disable this in the configure script, and we need
   # PCRE2 for R 4.x, we hide PCRE2 from the configure script by temporarily
   # removing the pkg-config file and pcre2-config script.
-  if [[ "${1}" =~ ^3 ]] && pkg-config --exists libpcre2-8; then
+  #
+  # The INCLUDE_PCRE2_IN_R_3 environment variable can be set to include PCRE2
+  # in R 3.x builds, for distributions where PCRE2 is always required.
+  # In Debian 11, Pango now depends on PCRE2, so R 3.x will not be compiled with
+  # Pango support if the PCRE2 pkg-config file is missing.
+  if [[ "${1}" =~ ^3 ]] && pkg-config --exists libpcre2-8 && [ -z "$INCLUDE_PCRE2_IN_R_3" ]; then
     mkdir -p /tmp/pcre2
     pc_dir=$(pkg-config --variable pcfiledir libpcre2-8)
     mv ${pc_dir}/libpcre2-8.pc /tmp/pcre2

builder/package.debian-11

@@ -4,10 +4,10 @@ if [[ ! -d /tmp/output/debian-11 ]]; then
   mkdir -p /tmp/output/debian-11
 fi
 
-# R 3.x requires PCRE1
-pcre_lib='libpcre2-dev'
+# R 3.x requires PCRE1. On Debian 11, R 3.x also requires PCRE2 for Pango support.
+pcre_lib_flags='-d libpcre2-dev'
 if [[ "${R_VERSION}" =~ ^3 ]]; then
-  pcre_lib='libpcre3-dev'
+  pcre_lib_flags='-d libpcre2-dev -d libpcre3-dev'
 fi
 
 fpm \
@@ -39,7 +39,7 @@ fpm \
   -d libpango-1.0-0 \
   -d libpangocairo-1.0-0 \
   -d libpaper-utils \
-  -d ${pcre_lib} \
+  ${pcre_lib_flags} \
   -d libpng16-16 \
   -d libreadline8 \
   -d libtcl8.6 \