Run autopep8 as well as clang-format when calling "make format",
the PATHS argument is passed to both utilities which will only operate on files they support.
For example: `make format PATHS=release/scripts` formats Python scripts, `make format PATHS=source/blender/blenlib` would format C/C++.
If users really want they can format C/C++ & Python files at the same time since both formatting utilities filter on file extension.
`make format PATHS="release/scripts/startup/nodeitems_builtins.py source/creator/creator.c"`
A LIBDIR variable has been added to the GNUmakefile to simplify references to this directory which can be one of 3 possible values.
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Notes:
- I wasn't able to use the Python binary in place (it gives an error that `libcrypt.so.1` isn't found), and didn't think it necessary to use the pre-compiled Python. So `PYTHON` will always be used to execute `autopep8.py` found in our `../lib/` directory. Otherwise the `autopep8` command will be used if none of the paths under `../lib/` are found.
- The checks for `../lib/*` are awkward, we could consider setting a single lib path and reusing that.
To check formatting does something, temporarily delete `./pyproject.toml` and run `make format`.