Creation of rayleigh lut directory fails when symlink is present in path

[mraspaud]

When the rayleigh luts are already downloaded and provided in a path containing a symlink, pyspectral crashes.

For example, if rayleigh_dir in the configuration is "/.local/share/pyspectral/rayleigh_only" and "pyspectral" is a symlink, the following error ensues:

  File "/opt/conda/lib/python3.13/site-packages/pyspectral/config.py", line 73, in get_config
    os.makedirs(config['rayleigh_dir'], exist_ok=True)
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen os>", line 228, in makedirs
FileExistsError: [Errno 17] File exists: '/.local/share/pyspectral/'