message: ci: fix missing -y in apt-install
diff: @@ -16,7 +16,7 @@ apt-get install -y g++-4.9
  wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -
  apt-add-repository "deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial main"
  apt-get update
  -apt-get install clang-5.0
  +apt-get install -y clang-5.0
  # 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
  