Update

Dockerfile

 # ENV PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 # ENV HOME /
 
+# Define Debian repos
 ARG DEB_RELEASE
 RUN printf '#------------------------------------------------------------------------------#\
 \n#                   OFFICIAL DEBIAN REPOS\
 \ndeb     http://deb.debian.org/debian-security	'${DEB_RELEASE}'/updates		main\
 \ndeb-src http://deb.debian.org/debian-security	'${DEB_RELEASE}'/updates		main\
 \n\
-\n# stretch-backports, previously on backports.debian.org\n\
+\n# stretch-backports, previously on backports.debian.org\
 \ndeb     http://ftp.debian.org/debian		'${DEB_RELEASE}'-backports	main\
 \ndeb-src http://ftp.debian.org/debian		'${DEB_RELEASE}'-backports	main\
-' >> /etc/apt/sources.list
-
-RUN cat /etc/apt/sources.list
-
+\n' > /etc/apt/sources.list
 
 # Build deps and clean up
 ARG BUILD_DEPS
     dpkg --add-architecture armhf && \
     apt-get -q  update && \
     apt-get -qy -o Dpkg::Use-Pty=0 upgrade && \
+    apt-get -qy -o Dpkg::Use-Pty=0 install --no-install-recommends apt-utils && \
     apt-get -qy -o Dpkg::Use-Pty=0 install --no-install-recommends ${BUILD_DEPS} \
         build-essential crossbuild-essential-armhf debhelper ca-certificates curl git iproute2 wget nano && \
     apt-get clean && rm -rf /var/lib/apt/lists/*