Add usd_decoder to mujoco/plugin.
- Previously was src/experimental/usd/usd_to_mjspec.cc, now that same spec is returned by the plugin.
PiperOrigin-RevId: 854350962
Change-Id: Ia980190a557c50ce8197980922a2594b613859b4
This will fetch and call the build_usd.py build helper for OpenUSD and build within the MuJoCo _deps folder. Simplifying the build process for MuJoCo with USD. Users can still provide their own USD build, but must now do so via pxr_DIR.
PiperOrigin-RevId: 846735578
Change-Id: I0da7eb2da6465e2d518084340e762bf370adb6d5