fix generation of Docker images (#1293)

.dockerignore

@@ -1,5 +1,5 @@
 # do not add .git, since it is needed to extract the tag
+# do not add /binaries, since they're needed by make dockerhub
 /tmp
-/binaries
 /coverage*.txt
 /apidocs/*.html

scripts/binaries.mk

@@ -22,6 +22,7 @@ COPY . ./
 
 ENV VERSION $(shell git describe --tags)
 ENV CGO_ENABLED 0
+RUN rm -rf binaries
 RUN mkdir tmp binaries
 RUN cp rtsp-simple-server.yml LICENSE tmp/