Merge pull request #3499 from azbarcea/master

fix llvm dependency from xenial to bionic on ubuntu:18.04

Docker/builder/Dockerfile

@@ -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 \