Fails to build with setuptools >= 61.0

[stratakis]

When trying to build x-tile with setuptools >= 61.0 this error message appears:

error: Multiple top-level packages discovered in a flat-layout: ['linux', 'glade', 'locale', 'debian', 'modules'].

To avoid accidental inclusion of unwanted files or directories,
setuptools will not proceed with this build.

If you are trying to create a single distribution with multiple packages
on purpose, you should not rely on automatic discovery.
Instead, consider the following options:

1. set up custom discovery (`find` directive with `include` or `exclude`)
2. use a `src-layout`
3. explicitly set `py_modules` or `packages` with a list of names

To find more information, look for "package discovery" on setuptools docs.

It can be fixed by adding packages=[] or py_modules=[] at the setup section of setup.py

See also pypa/setuptools#3197 (comment)

[giuspen]

thanks