Add qemu-user

Dockerfile

 FROM ubuntu:oracular
 
-RUN apt update && apt install -y ca-certificates openssh-server python3-pip python3-dev xxd file  \
+RUN apt update && apt install -y ca-certificates openssh-server python3-pip python3-dev xxd file qemu-user \
                                 libssl-dev libffi-dev build-essential binutils-multiarch git gdb gdb-multiarch ltrace strace tmux wget curl && \
                                 apt clean && rm -rf /var/lib/apt/lists/* && touch /root/.hushlogin