Feed the XML to anv_extensions.py and anv_entrypoints_gen.py.
Do it on all platforms, not just Android. Tested on Android and Fedora.

We always parse the Android XML, regardless of target platform, to
help reduce the chance that people working on non-Android break the
Android build.

v2:
  - Squash in Tapani's changes to Android.*.mk.

Reviewed-by: Tapani Pälli <tapani.palli@intel.com> (v1)