ARROW-6171: [R][CI] Fix R library search path

This was introduced when the base docker C++ image also installed lz4 from packages and not just conda. Also fixes a cmake warning.

Closes #5295 from fsaintjacques/ARROW-6171-docker-r and squashes the following commits:

8bcfaa0 <François Saint-Jacques> ARROW-6171:  Fix R library search path

Authored-by: François Saint-Jacques <[email protected]>
Signed-off-by: Wes McKinney <[email protected]>

ci/docker_build_cpp.sh

@@ -35,7 +35,7 @@ cmake -GNinja \
       -DCMAKE_CXX_FLAGS=${CXXFLAGS:-} \
       -DARROW_DEPENDENCY_SOURCE=${ARROW_DEPENDENCY_SOURCE:-AUTO} \
       -DARROW_VERBOSE_THIRDPARTY_BUILD=${ARROW_VERBOSE_THIRDPARTY_BUILD:-OFF} \
-      -DARROW_BUILD_WARNING_LEVEL=${DARROW_BUILD_WARNING_LEVEL:-CHECKIN} \
+      -DBUILD_WARNING_LEVEL=${DARROW_BUILD_WARNING_LEVEL:-CHECKIN} \
       -DARROW_BUILD_TESTS=${ARROW_BUILD_TESTS:-ON} \
       -DARROW_BUILD_BENCHMARKS=${ARROW_BUILD_BENCHMARKS:-ON} \
       -DARROW_BUILD_UTILITIES=${ARROW_BUILD_UTILITIES:-ON} \

r/Dockerfile

@@ -80,6 +80,13 @@ RUN Rscript -e "install.packages(c( \
         'lubridate'), \
         repos = 'https://cran.rstudio.com')"
 
+# ARROW-6171: Because lz4 is installed in the base Ubuntu image, there's an
+# issue of which library is loaded at runtime. R by default will override
+# LD_LIBRARY_PATH at runtime by concatenating (in that order)
+# R_LD_LIBRARY_PATH, R_JAVA_LD_LIBRARY_PATH and LD_LIBRARY_PATH. If
+# R_LD_LIBRARY_PATH is not set, it'll default to a list of directories which
+# contains /usr/lib/x86_64-linux-gnu.
+ENV R_LD_LIBRARY_PATH=$LD_LIBRARY_PATH
 
 # build, install, test R package
 CMD ["/bin/bash", "-c", "/arrow/ci/docker_build_cpp.sh && \