Dockerfile: use nearby mirrors for packages
Many Contiki-NG users are outside the US,
switch the packages to be downloaded from
a mirror that is closer to the user.
@@ -6,7 +6,8 @@ ENV DEBIAN_FRONTEND noninteractive
USER root
# Tools
-RUN apt-get -qq update && \
+RUN sed -i -e 's#http://archive.ubuntu.com/ubuntu/#mirror://mirrors.ubuntu.com/mirrors.txt#' /etc/apt/sources.list && \
+ apt-get -qq update && \
apt-get -qq -y --no-install-recommends install gnupg ca-certificates software-properties-common > /dev/null
RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF && \
