Use debian slim for docker builds (#828)

* Use debian slim for docker builds

* changelog

* Update 828.bugfix

Dockerfile

-FROM node:16-alpine AS BUILD
+FROM node:16-slim AS BUILD
 COPY . /tmp/src
 # install some dependencies needed for the build process
-RUN apk add --no-cache -t build-deps make gcc g++ python3 ca-certificates libc-dev wget git
+RUN apt update && apt install -y build-essential make gcc g++ python3 ca-certificates libc-dev wget git
 
 # Workaround for https://github.com/matrix-org/matrix-appservice-discord/issues/803
 RUN git config --global url.https://github.com/.insteadOf git://github.com/
@@ -9,7 +9,7 @@ RUN git config --global url.https://github.com/.insteadOf git://github.com/
 RUN cd /tmp/src \
     && yarn
 
-FROM node:16-alpine
+FROM node:16-slim
 ENV NODE_ENV=production
 COPY --from=BUILD /tmp/src/build /build
 COPY --from=BUILD /tmp/src/config /config

changelog.d/828.bugfix

+Fix Docker instances not starting due to being unable to load a dynamic library in the latest unstable image.