message: ci: select gcov-7 for consistency with gcc-7 in Docker image.
  This is needed to enable Bazel native coverage (without, we don't get
  coverage files generated).
  Risk level: Low
  Testing: bazel coverage run inside CI image.
diff: @@ -18,8 +18,10 @@ apt update
  apt install -y g++-7
  update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-7 1000
  update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 1000
  +update-alternatives --install /usr/bin/gcov gcov /usr/bin/gcov-7 1000
  update-alternatives --config gcc
  update-alternatives --config g++
  +update-alternatives --config gcov
  # Bazel and related dependencies.
  apt-get install -y openjdk-8-jdk curl
  echo "deb [arch=amd64] http://storage.googleapis.com/bazel-apt stable jdk1.8" | tee /etc/apt/sources.list.d/bazel.list
  