Split Dockerfile to build and runtime phases to cut down image size

Dockerfile

-FROM ubuntu:22.04
+ARG BASE_IMAGE=ubuntu:22.04
+FROM $BASE_IMAGE AS runtime_base
+MAINTAINER Petr Spacek <pspacek@isc.org>
 ENV DEBIAN_FRONTEND=noninteractive
-RUN \
-	apt-get update -qq && \
-	apt-get install -y -qqq software-properties-common && \
-	add-apt-repository -y ppa:dns-oarc/dnsjit && \
-	apt-get update -qq && \
-	apt-get install -y -qqq \
-		dnsjit \
-		dnsjit-dev \
-		python3 \
-		python3-pip \
-		tshark \
-		jq \
-		libnghttp2-dev \
-		luajit \
-		libuv1-dev \
-		make \
-		cmake \
-		ninja-build \
-		pkg-config \
-		git && \
-	rm -rf /var/lib/apt/lists/*
 
+RUN apt-get update -q
+RUN apt-get upgrade -y -q
+# required for PPA repo usage
+RUN apt-get install -y -q -o APT::Install-Suggests=0 -o APT::Install-Recommends=0 \
+	ca-certificates \
+	lsb-release
+
+# avoid PGP; keyring download here would have dependency on TLS anyway
+# and I don't want to hardcode PGP key ID here
+RUN echo "deb [trusted=yes] https://ppa.launchpadcontent.net/dns-oarc/dnsjit/ubuntu `lsb_release -c -s` main" > /etc/apt/sources.list.d/dns-oarc.list
+RUN apt-get update -q
+
+# shotgun's runtime depedencies
+RUN apt-get install -y -q -o APT::Install-Suggests=0 -o APT::Install-Recommends=0 \
+	dnsjit \
+	libnghttp2-14 \
+	libuv1 \
+	python3 \
+	python3-pip
+
+COPY requirements.txt /tmp/requirements.txt
+RUN pip3 install -r /tmp/requirements.txt
+
+# separate image for build, will not be tagged at the end
+FROM runtime_base AS build_stage
+RUN apt-get install -y -q -o APT::Install-Suggests=0 -o APT::Install-Recommends=0 \
+	cmake \
+	dnsjit-dev \
+	g++ \
+	gcc \
+	git \
+	jq \
+	libnghttp2-dev \
+	libuv1-dev \
+	ninja-build \
+	pkg-config \
+	tshark
+
+COPY . /shotgun
+RUN mkdir /shotgun/replay/dnssim/build
+WORKDIR /shotgun/replay/dnssim/build
+RUN cmake .. -DCMAKE_BUILD_TYPE=Release -G Ninja
+RUN cmake --build .
+RUN cmake --install .
+
+# copy only installed artifacts, Shotgun repo and throw away everything else
+FROM runtime_base AS installed
+COPY --from=build_stage /usr/local /usr/local
 COPY . /shotgun
 WORKDIR /shotgun
 ENV PATH="${PATH}:/shotgun"
-RUN cd replay/dnssim && \
-  mkdir build && \
-  cd build && \
-  cmake .. -DCMAKE_BUILD_TYPE=Release -G Ninja && \
-  cmake --build . && \
-  cmake --install . && \
-  cd /shotgun
-RUN pip3 install -r requirements.txt
+
+# cleanup intended for docker build --squash
+RUN rm -rf /shotgun/.git