Build IWYU for LLVM 7 in iwyu docker-compose job

Change-Id: I3bf8bd27728094656e81af480de607853259c694

dev/lint/Dockerfile

@@ -21,12 +21,10 @@ RUN apt-get install -y -q gnupg && \
     apt update && \
     apt-get install -y -q \
       clang-7 \
+      libclang-7-dev \
       clang-format-7 \
       clang-tidy-7 \
       clang-tools-7
 
 RUN conda install flake8 && \
     conda clean --all -y
-
-# https://bugs.launchpad.net/ubuntu/+source/iwyu/+bug/1769334
-RUN ln -sv /usr/lib/clang/6.0 /usr/lib/clang/5.0.1

dev/lint/run_iwyu.sh

@@ -22,15 +22,34 @@ mkdir -p /build/lint
 pushd /build/lint
 
 cmake -GNinja \
+      -DARROW_FLIGHT=ON \
+      -DARROW_GANDIVA=ON \
       -DARROW_PARQUET=ON \
       -DARROW_PYTHON=ON \
       -DCMAKE_CXX_FLAGS='-D_GLIBCXX_USE_CXX11_ABI=0' \
       -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
       /arrow/cpp
-# Make so that vendored bits are built
-ninja arrow_shared
 
 popd
 
+# Build IWYU for current Clang
+git clone https://github.com/include-what-you-use/include-what-you-use.git
+pushd include-what-you-use
+git checkout clang_7.0
+popd
+
+export CC=clang-7
+export CXX=clang++-7
+
+mkdir -p iwyu
+pushd iwyu
+cmake -G "Unix Makefiles" \
+      -DCMAKE_PREFIX_PATH=/usr/lib/llvm-7 \
+      ../include-what-you-use
+make -j4
+popd
+
+export PATH=`pwd`/iwyu/bin:$PATH
+
 export IWYU_COMPILATION_DATABASE_PATH=/build/lint
 /arrow/cpp/build-support/iwyu/iwyu.sh all

docker-compose.yml

@@ -207,9 +207,6 @@ services:
     #   docker-compose build lint
     #   docker-compose run iwyu
     image: arrow:lint
-    environment:
-      CC: clang
-      CXX: clang++
     command: arrow/dev/lint/run_iwyu.sh
     volumes: *ubuntu-volumes