build: enable upx for cleardns, fix upx/upx#617

Dockerfile

@@ -56,6 +56,8 @@ COPY --from=to-json /libto_json.a /cleardns/src/to-json/target/release/
 WORKDIR /cleardns/bin/
 RUN cmake -DCMAKE_EXE_LINKER_FLAGS=-static -DCMAKE_BUILD_TYPE=Release .. && make
 RUN strip cleardns && mv cleardns /tmp/
+COPY --from=upx /tmp/upx /usr/bin/
+RUN upx -9 /tmp/cleardns
 
 FROM ${ALPINE} AS build
 RUN apk add xz