01-copy-manifests-dir: Permission denied for non-root user

[Mark Goddard]

When building an image with the `manifests` element as a non-root user, the image fails to build. This affects the Ironic Python Agent (IPA) image.

# Steps to reproduce

Seen using a Rocky Linux 9.3 host with diskimage-builder 3.33.0. The host has had the https://github.com/ansible-lockdown/RHEL9-CIS Ansible role applied which applies changes to meet the CIS security benchmarks. I was unable to reproduce the issue on a similar host that had not had the CIS changes applied.

python3 -m venv venv
source venv/bin/activate
pip install diskimage-builder ironic-python-agent-builder
ironic-python-agent-builder --release 9-stream centos

# Expected results

Image builds successfully.

# Actual results

Image fails to build

'/tmp/dib_build.67Z4UrNX/mnt//etc/dib-manifests' -> 'ipa.d/dib-manifests'
cp: cannot access '/tmp/dib_build.67Z4UrNX/mnt//etc/dib-manifests': Permission denied

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/diskimage-builder/+/922385