setup.py omits assets when kivymd is in directory path

[charliermarsh]

If you build kivymd from a directory that has kivymd in the path, the .kv and other asset files are omitted, as out_files.append(filepath.split(f"kivymd{os.sep}")[1]) (in setup.py) truncates at the first instance of kivymd.

For example: running python -m build from ~/workspace/kivymd/foo creates kivymd-2.0.1.dev0.tar.gz without any .kv files in it. While running from ~/workspace/bar/foo/ includes the .kv files.