Use Ubuntu 17.10 as the base image

ci/docker/aarch64-unknown-linux-gnu/Dockerfile

ci/docker/arm-unknown-linux-gnueabihf/Dockerfile

ci/docker/i686-unknown-linux-gnu/Dockerfile

ci/docker/i686-unknown-linux-musl/Dockerfile

ci/docker/mips-unknown-linux-gnu/Dockerfile

ci/docker/mips-unknown-linux-musl/Dockerfile

ci/docker/mips64-unknown-linux-gnuabi64/Dockerfile

ci/docker/mipsel-unknown-linux-musl/Dockerfile

ci/docker/powerpc-unknown-linux-gnu/Dockerfile

ci/docker/powerpc64-unknown-linux-gnu/Dockerfile

ci/docker/s390x-unknown-linux-gnu/Dockerfile

ci/docker/x86_64-unknown-linux-gnu/Dockerfile

ci/docker/x86_64-unknown-linux-musl/Dockerfile