ArchConfigHandler reads --config and --creds from sys.argv via argparse at
construction time; it ignores ARCHINSTALL_CONFIG/ARCHINSTALL_CREDS env
vars (confirmed in archinstall 4.3 lib/args.py:_parse_args). Setting those
env vars was a no-op, so handler.config.disk_config was always None when
the wrapper stripped our args off the real argv.
Fix: build a synthetic argv [prog, --config <path>, --creds <path>] and
swap it into sys.argv just for the ArchConfigHandler() call, then
restore. Drops the unused 'import os' now that the env var lines are
gone.
Ryan Hughes
b568b0b796