Otherwise these resources are not packaged and cannot be included.
E.g., `mkosi-initrd` fails because it adds `--include=mkosi-initrd`:
```
$ mkosi-initrd
Traceback (most recent call last):
File "/usr/lib/python3.11/site-packages/mkosi/run.py", line 64, in uncaught_exception_handler
yield
File "/usr/lib64/python3.11/contextlib.py", line 81, in inner
return func(*args, **kwds)
^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/site-packages/mkosi/__main__.py", line 30, in main
args, images = parse_config(sys.argv[1:], resources=resources)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/site-packages/mkosi/config.py", line 3907, in parse_config
context.parse_new_includes()
File "/usr/lib/python3.11/site-packages/mkosi/config.py", line 3575, in parse_new_includes
st = path.stat()
^^^^^^^^^^^
File "/usr/lib64/python3.11/pathlib.py", line 1013, in stat
return os.stat(self, follow_symlinks=follow_symlinks)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpyqqy4ttp/resources/mkosi-initrd'
```
Fixes
9f48afa4a76b6002edc90ac976a2d1e8fd01f793