Add setuptools to tkcalendar

[nashamri]

Hello there 👋

I was trying to build a project that had a dependency on tkcalendar and I got this error:

λ nix build
error: builder for '/nix/store/b9dplp5dfmdf8ywg3l0c3awj10vdivkn-python3.10-tkcalendar-1.6.1.drv' failed with exit code 2;
       last 10 log lines:
       >   File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
       >   File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
       >   File "<frozen importlib._bootstrap>", line 992, in _find_and_load_unlocked
       >   File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
       >   File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
       >   File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
       >   File "<frozen importlib._bootstrap>", line 1004, in _find_and_load_unlocked
       > ModuleNotFoundError: No module named 'setuptools'
       > 

So, this is just to add setuptools to the list of build-systems.