support/docker: use APT::Retries in apt-get calls to retry

snapshot.debian.org is notoriously slow, and quite often leads to
timeouts when downloading packages. To give us a better chance of
succeeding, let's retry 3 times before failing.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

support/docker/Dockerfile

@@ -20,8 +20,8 @@ COPY apt-sources.list /etc/apt/sources.list
 
 # The container has no package lists, so need to update first
 RUN dpkg --add-architecture i386 && \
-    apt-get update -y
-RUN apt-get install -y --no-install-recommends \
+    apt-get -o APT::Retries=3 update -y
+RUN apt-get -o APT::Retries=3 install -y --no-install-recommends \
         bc \
         build-essential \
         bzr \