Put R build steps into a separate CI script

ci/docker_build_r.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+set -e
+
+export ARROW_BUILD_TOOLCHAIN=$CONDA_PREFIX
+export ARROW_HOME=$CONDA_PREFIX
+
+# For newer GCC per https://arrow.apache.org/docs/python/development.html#known-issues
+export CXXFLAGS="-D_GLIBCXX_USE_CXX11_ABI=0"
+
+# Build arrow
+pushd /arrow/r
+
+Rscript -e "Rcpp::compileAttributes()"
+R CMD build --keep-empty-dirs .
+R CMD INSTALL $(ls | grep arrow_*.tar.gz)
+R CMD check $(ls | grep arrow_*.tar.gz) --as-cran
+
+popd

r/Dockerfile

@@ -59,7 +59,4 @@ ENV LD_LIBRARY_PATH=/opt/conda/lib/:/build/cpp/src/arrow:/arrow/r/src
 
 # build, install, test R package
 CMD /arrow/ci/docker_build_cpp.sh && \
-    Rscript -e "Rcpp::compileAttributes('/arrow/r')" && \
-    R CMD build --keep-empty-dirs /arrow/r && \
-    R CMD INSTALL $(ls | grep arrow_*.tar.gz) && \
-    R CMD check $(ls | grep arrow_*.tar.gz) --as-cran
+    /arrow/ci/docker_build_r.sh