message: fix llvm dependency from xenial to bionic on ubuntu:18.04
diff: @@ -8,7 +8,7 @@ RUN echo 'APT::Install-Recommends 0;' >> /etc/apt/apt.conf.d/01norecommends \
  && apt-get update \
  && DEBIAN_FRONTEND=noninteractive apt-get install -y sudo wget curl net-tools ca-certificates unzip gnupg
  -RUN echo "deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-4.0 main" >> /etc/apt/sources.list.d/llvm.list \
  +RUN echo "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main" >> /etc/apt/sources.list.d/llvm.list \
  && wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add - \
  && apt-get update \
  && DEBIAN_FRONTEND=noninteractive apt-get install -y git-core automake autoconf libtool build-essential pkg-config libtool \
  