Add Scala Native build dependencies to the Docker image

Reduces the size of the image by ~200MB by only installing required
packages (via --no-install-recommends) and uses modern apt-key features
to fetch the LLVM repo key.

Author: jonas

Dockerfile

@@ -2,24 +2,30 @@ ARG UBUNTU_VERSION=18.04
 FROM ubuntu:$UBUNTU_VERSION
 
 RUN set -x \
+ && : Remove pre-bundled libunwind \
+ && find /usr -name "*libunwind*" -delete \
  && apt update \
- && apt install -y apt-transport-https gnupg2 ca-certificates \
+ && apt install -y --no-install-recommends apt-transport-https gnupg2 ca-certificates \
  && echo "deb https://dl.bintray.com/sbt/debian /" > /etc/apt/sources.list.d/sbt.list \
  && apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 2EE0EA64E40A89B84B2DF73499E82A75642AC823 \
  && apt update \
- && apt install -y curl build-essential openjdk-8-jdk-headless sbt cmake make clang-format-5.0 \
+ && apt install -y --no-install-recommends \
+            g++ openjdk-8-jdk-headless sbt cmake make curl git \
+            libgc-dev libunwind8-dev libre2-dev \
  && rm -rf /var/lib/apt/lists/*
 
 ARG LLVM_VERSION=6.0
 ENV LLVM_VERSION=$LLVM_VERSION
 # LLVM dev versions do not have a "-x.y" version suffix.
 ARG LLVM_DEB_COMPONENT=-$LLVM_VERSION
 RUN set -x \
- && curl https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add - \
  && . /etc/lsb-release \
  && echo "deb https://apt.llvm.org/$DISTRIB_CODENAME/ llvm-toolchain-$DISTRIB_CODENAME$LLVM_DEB_COMPONENT main" > /etc/apt/sources.list.d/llvm.list \
+ && apt-key adv --fetch-keys https://apt.llvm.org/llvm-snapshot.gpg.key \
  && apt update \
- && apt install -y clang-$LLVM_VERSION libclang-$LLVM_VERSION-dev \
+ && apt install -y --no-install-recommends \
+            clang-$LLVM_VERSION clang-format-$LLVM_VERSION \
+            libclang-$LLVM_VERSION-dev llvm-$LLVM_VERSION-dev \
  && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /src