Update docker images to bionic and llvm-8 (#49)

Author: Brian J. Cardiff

docker/Dockerfile

@@ -5,8 +5,9 @@ RUN \
   apt-get update && \
   apt-get install -y apt-transport-https && \
   apt-get update && \
-  apt-get install -y tzdata gcc pkg-config libssl-dev libxml2-dev libyaml-dev libgmp-dev git make && \
-  apt-get install -y libpcre3-dev libevent-dev && \
+  DEBIAN_FRONTEND=noninteractive \
+  apt-get install -y tzdata gcc pkg-config libssl-dev libxml2-dev libyaml-dev libgmp-dev git make \
+                     libpcre3-dev libevent-dev && \
   apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 ARG crystal_deb
@@ -20,7 +21,7 @@ FROM runtime as build
 
 RUN \
   apt-get update && \
-  apt-get install -y build-essential llvm-4.0 libedit-dev libreadline-dev gdb && \
+  apt-get install -y build-essential llvm-8 libedit-dev libreadline-dev gdb && \
   apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 ENV LIBRARY_PATH=/usr/lib/crystal/lib/

docker/Makefile

@@ -4,8 +4,8 @@ DOCKER_TAG ?=        ## How to tag the docker image. a -build will be appended f
 DOCKER_REPOSITORY ?= ## Docker hub repository to commit image
 
 OUTPUT_DIR = build
-BUILD_ARGS64 = --build-arg crystal_deb=./tmp/crystal.deb --build-arg base_docker_image=ubuntu:xenial
-BUILD_ARGS32 = --build-arg crystal_deb=./tmp/crystal.deb --build-arg base_docker_image=i386/ubuntu:xenial
+BUILD_ARGS64 = --build-arg crystal_deb=./tmp/crystal.deb --build-arg base_docker_image=ubuntu:bionic
+BUILD_ARGS32 = --build-arg crystal_deb=./tmp/crystal.deb --build-arg base_docker_image=i386/ubuntu:bionic
 
 .PHONY: all64
 all64: $(OUTPUT_DIR)/docker-$(CRYSTAL_VERSION).tar.gz $(OUTPUT_DIR)/docker-$(CRYSTAL_VERSION)-build.tar.gz