libxml2: Disable python on windows builds entirely.
libxml2: Disable python on windows builds entirely.

Disable the python module in libxml2 regardless of cross-compiling
or not.

centricular/cerbero,GStreamer/cerbero,atsushieno/cerbero,fluendo/cerbero,GStreamer/cerbero,nirbheek/cerbero,centricular/cerbero,fluendo/cerbero,centricular/cerbero,nirbheek/cerbero,centricular/cerbero,fluendo/cerbero,atsushieno/cerbero,GStreamer/cerbero,fluendo/cerbero,nirbheek/cerbero,GStreamer/cerbero,atsushieno/cerbero,centricular/cerbero,atsushieno/cerbero,nirbheek/cerbero,atsushieno/cerbero,GStreamer/cerbero,fluendo/cerbero