Set PAGER for Ubuntu and Debian only

/usr/bin/pager is specific to Debian/Ubuntu. For other OSs, use the default
pager detected by the configure script, which will either be less or more.

See https://github.com/rstudio/r-builds/issues/3

builder/Dockerfile.debian-9

@@ -13,5 +13,8 @@ RUN pip install awscli
 
 RUN chmod 0777 /opt
 
+# Override the default pager used by R
+ENV PAGER /usr/bin/pager
+
 COPY build.sh .
 ENTRYPOINT ./build.sh

builder/Dockerfile.ubuntu-1604

@@ -13,5 +13,8 @@ RUN pip install awscli
 
 RUN chmod 0777 /opt
 
+# Override the default pager used by R
+ENV PAGER /usr/bin/pager
+
 COPY build.sh .
 ENTRYPOINT ./build.sh

builder/Dockerfile.ubuntu-1804

@@ -13,5 +13,8 @@ RUN pip install awscli
 
 RUN chmod 0777 /opt
 
+# Override the default pager used by R
+ENV PAGER /usr/bin/pager
+
 COPY build.sh .
 ENTRYPOINT ./build.sh

builder/build.sh

@@ -73,7 +73,6 @@ compile_r() {
   # set some common environment variables for the configure step
   AWK=/usr/bin/awk \
   LIBnn=lib \
-  PAGER=/usr/bin/pager \
   PERL=/usr/bin/perl \
   R_PDFVIEWER=xdg-open \
   R_BROWSER=xdg-open \