Download Docker images first as that seems to work better at least locally

ci/run-docker.sh

@@ -7,6 +7,14 @@ set -ex
 
 run() {
     echo "Building docker container for target ${1}"
+
+    # FIXME: Hacky workaround. Docker build seems to work better if we pull the base images first
+    ubuntu_images=( 16.04 17.10 18.04 )
+    for i in "${ubuntu_images[@]}"
+    do
+      docker pull ubuntu:$i
+    done
+
     # use -f so we can use ci/ as build context
     docker build -t libc -f "ci/docker/${1}/Dockerfile" ci/
     mkdir -p target