This is an attempt at generating the font metrics from publicly downloadable data.
The Windows metrics are generated from the AFM sources instead of being copied from some unrelated TrueType fonts as done in a3b562f74eeb6a5abc3013e57ff489107677b743. It's not clear if that matters, neither seem to match the values on Windows.
It would be possible to simplify things further, and to use more up-to-date source data, but for now the goal is to minimize the diff to the generated files.