cdbba15c6c
This avoids touching the output file when it hasn't changed. The cmake build integration now uses this so that touching a .yaml or .h.def file in ways that don't affect the generated header output won't cause unnecessary recompilations.
This directory also contains the Python sources for hdrgen, which is what generates the headers public libc headers. The definitions for these headers are in the ``include`` directory. The ``.h.def`` files are the bases and the ``.yaml`` files are the contents.