`openexr_skbuild_plugin.py` adds an unnecessary `cmake` build requirement

[mgorny]

openexr/src/wrappers/python/openexr_skbuild_plugin.py

Lines 103 to 106 in 66158f8

	def get_requires_for_dynamic_metadata(
	_settings: Optional[Dict[str, object]] = None,
	) -> List[str]:
	return ["cmake"]

This code is unconditionally adding a dependency on cmake PyPI project. This is inconsistent with how scikit-build-core operates, as it prefers using system CMake and adds the dependency only if it can't find a working version. However, the plugin effectively forces it to use the version from PyPI which is less portable, as it lacks downstream patching.

Given that scikit-build-core requires CMake by its purpose, I don't really understand why the plugin would need to add a dependency in the first place. And if you really to do it, I think it would be better to use the same approach as scikit-build-core does, i.e.:

https://github.com/scikit-build/scikit-build-core/blob/4fbd3b702db5157fa8c742b6c799a60adfb038e5/src/scikit_build_core/build/__init__.py#L154-L164