there's no need for a two stage build

Dockerfile

@@ -4,10 +4,6 @@ FROM ${BASE_IMAGE}:${ALPINE_VERSION}
 MAINTAINER "f <f@sutty.nl>"
 
 COPY ./syncthing_start.sh /usr/local/bin/syncthing_start
-RUN chmod 755 /usr/local/bin/syncthing_start
-
-FROM ${BASE_IMAGE}:${ALPINE_VERSION}
-ARG ALPINE_VERSION
 
 # Syncthing runs with Sutty's uid and gid so ownership is kept, because
 # they are not synced.
@@ -17,7 +13,6 @@ RUN adduser -s /bin/sh -G syncthing -D -u 1000 -h /home/syncthing syncthing
 RUN apk add --no-cache ca-certificates daemonize syncthing
 
 COPY ./monit.conf /etc/monit.d/syncthing.conf
-COPY --from=build /usr/local/bin/syncthing_start /usr/local/bin/syncthing_start
 
 EXPOSE 22000
 EXPOSE 22000/udp