towerpark

Logs generated before calling `LearnerBuilder::build` are discarded in some examples

2

**Describe the bug** In some examples, logs generated before calling `LearnerBuilder::build` don't get saved to the log file. Some of the examples affected by this issue are: [mnist](https://github.com/tracel-ai/burn/blob/6dbc3fd295c8c84009f32c012f4161bd81106b73/examples/mnist/src/training.rs#L43), [text_classification](https://github.com/tracel-ai/burn/blob/6dbc3fd295c8c84009f32c012f4161bd81106b73/examples/text-classification/src/training.rs#L43), [text_generation](https://github.com/tracel-ai/burn/blob/6dbc3fd295c8c84009f32c012f4161bd81106b73/examples/text-generation/src/training.rs#L35)....