ERROR: failed to build: failed to solve: pull access denied, repository does not exist or may require authorization: server message: insufficient_scope: authorization failed

## Description

A clear description of the bug.

## Steps to Reproduce

1. Use the [published procedure][pp] to build all containers: `image-build/scripts/build-images.sh --target all`

[pp]: https://googlecloudplatform.github.io/scion/advanced-local/custom-images/#option-1-local-docker-build

## Expected Behavior

Containers are built with success

## Actual Behavior

Error:

```
core-base done.
==> [local-docker] building scion-base...
[+] Building 0.6s (5/5) FINISHED docker-container:scion-builder
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 4.27kB 0.0s
=> resolve image config for docker-image://docker.io/docker/dockerfile:1 0.1s
=> CACHED docker-image://docker.io/docker/dockerfile:1@sha256:2780b5c3bab67f1f76c781860de469442999ed1a0d7992a5efdf2cffc0e3d769 0.0s
=> => resolve docker.io/docker/dockerfile:1@sha256:2780b5c3bab67f1f76c781860de469442999ed1a0d7992a5efdf2cffc0e3d769 0.0s
=> ERROR [internal] load metadata for docker.io/library/core-base:1d56231f 0.2s
=> [auth] library/core-base:pull token for registry-1.docker.io 0.0s
------
> [internal] load metadata for docker.io/library/core-base:1d56231f:
------

1 warning found (use docker --debug to expand):
- InvalidDefaultArgInFrom: Default value for ARG ${BASE_IMAGE} results in empty or invalid base image name (line 18)
Dockerfile:18
--------------------
16 | # Scion Base Image - Adds sciontool and scion user on top of core-base
17 | ARG BASE_IMAGE
18 | >>> FROM ${BASE_IMAGE} AS base
19 |
20 | # Builder stage for sciontool compilation
--------------------
ERROR: failed to build: failed to solve: pull access denied, repository does not exist or may require authorization: server message: insufficient_scope: authorization failed
```

Run image-build/scripts/build-images.sh --target all using the published custom-images procedure, then inspect the Dockerfile at line 18 and the image-build script's BASE_IMAGE handling. Confirm that the core-base and scion-base containers, along with the other targets, build successfully without the authorization error.

Written by the indexing model from the issue text.