Function flake_settings_add_to_eval_state_builder 

pub unsafe extern "C" fn flake_settings_add_to_eval_state_builder(
    context: *mut c_context,
    settings: *mut flake_settings,
    builder: *mut eval_state_builder,
) -> err

@brief Initialize a nix_flake_settings to contain builtins.getFlake and potentially more.

@warning This does not put the eval state in pure mode!

@param[out] context Optional, stores error information @param[in] settings The settings to use for e.g. builtins.getFlake @param[in] builder The builder to modify