ci(docker): using docker build args instead of extra dockerfile for ffmpeg (#6989)

* build: using docker build arg to determine install ffmpeg or not

* ci: pass build-args to ffmpeg image build step

Dockerfile

@@ -8,16 +8,23 @@ COPY ./ ./
 RUN bash build.sh release docker
 
 FROM alpine:edge
+
+ARG INSTALL_FFMPEG=false
 LABEL MAINTAINER="i@nn.ci"
-VOLUME /opt/alist/data/
+
 WORKDIR /opt/alist/
-COPY --from=builder /app/bin/alist ./
-COPY entrypoint.sh /entrypoint.sh
+
 RUN apk update && \
     apk upgrade --no-cache && \
     apk add --no-cache bash ca-certificates su-exec tzdata; \
-    chmod +x /entrypoint.sh && \
+    [ "$INSTALL_FFMPEG" = "true" ] && apk add --no-cache ffmpeg; \
     rm -rf /var/cache/apk/*
+
+COPY --from=builder /app/bin/alist ./
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh && /entrypoint.sh version
+
 ENV PUID=0 PGID=0 UMASK=022
+VOLUME /opt/alist/data/
 EXPOSE 5244 5245
 CMD [ "/entrypoint.sh" ]