optimize docker build

Signed-off-by: NRoland.Ma <rolandma@yunify.com>

.dockerignore

-tmp/
-.github
+# exclude all files and folders except bin folder
+**
+!bin

build/ks-controller-manager/Dockerfile

@@ -3,10 +3,10 @@
 # that can be found in the LICENSE file.
 FROM alpine:3.11
 
-COPY  /bin/cmd/controller-manager /usr/local/bin/
-
 RUN apk add --no-cache ca-certificates
 
+COPY  /bin/cmd/controller-manager /usr/local/bin/
+
 EXPOSE 8443 8080
 
 CMD ["sh"]
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