ZT_dockerfile tweak

ZT_docker/Dockerfile

@@ -16,7 +16,7 @@ RUN echo -e "no\n/opt/intel" | ./sgx_linux_x64_psw_*.bin
 WORKDIR /pir/
 COPY ZT.tar.gz /pir/
 RUN tar -xf ZT.tar.gz
-COPY start-aesmd /usr/local/sbin/
+RUN cp start-aesmd /usr/local/sbin/
 
 RUN git clone https://github.com/openssl/openssl.git OpenSSL_1.1.1d && \
 	cd OpenSSL_1.1.1d && git checkout tags/OpenSSL_1_1_1d && \