`set -e` aborted build.sh when `podman image rm`/`prune` failed, and
`2>/dev/null` hid the reason, so --remove exited 125 with no output.
Combining --remove --prune also skipped the prune.
Guard the removal with `podman image exists` for a clear "nothing to
remove", drop `2>/dev/null` so podman's reason is visible, and use
`cmd || echo` to warn without aborting. Exit status stays 0 on failure
by design.
- Default ubuntu user is removed
- Can add apt packages during image building with --apt-packages="list
of pkg"
- Remove and/or prune podman image option
- Fix condition checks
Ian