Use Ubuntu 20.04 for Bazel Docker container
# ATTENTION: use the build.sh script to build this image.
# ./build.sh <OCI_REPOSITORY> <BAZEL_VERSION>
-FROM ubuntu:16.04 AS base_image
+FROM ubuntu:20.04 AS base_image
RUN --mount=source=bazel/oci/install_packages.sh,target=/mnt/install_packages.sh,type=bind \
/mnt/install_packages.sh
