Remove all unnecessary vertcoin binaries

Dockerfile

@@ -6,9 +6,9 @@ ADD ./bin /usr/local/bin
 RUN chmod a+x /usr/local/bin/* && \
     apt-get update && \
     apt-get install -y --no-install-recommends curl ca-certificates unzip && \
-    curl -L https://github.com/vertcoin/vertcoin/releases/download/v0.11.1.0/vertcoin-v0.11.1.0-linux-64bit.zip --output prebuilt.zip && \
-    unzip prebuilt.zip && \
-    mv vertcoind /usr/local/bin && \
+    curl -L https://github.com/vertcoin/vertcoin/releases/download/v0.11.1.0/vertcoin-v0.11.1.0-linux-64bit.zip --output /tmp/prebuilt.zip && \
+    unzip /tmp/prebuilt.zip -d /tmp && \
+    mv /tmp/vertcoind /usr/local/bin && \
     apt-get purge -y curl ca-certificates unzip && \
     apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*