Improves output from tests comparing export results to the golden example file: - Prints which of the files that are empty and/or has no newline. - Prints a message when there is a mismatch in file length. - Clarifies that the inner compare loop only compares up to shortest string. - Prints the name of the failing golden file, indicating if it was the obj or mtl file that failed. Pull Request: https://projects.blender.org/blender/blender/pulls/141958