Port of NxEngine to the libretro API. NXEngine is a Cave Story game
engine clone.

It will require Cave Story 1.0.0.6 and the Aeon Genesis translation
which can be download from the RetroArch downloadable content.

Alternatively Cave Story is available from Studio Pixel's website:
https://studiopixel.sakura.ne.jp/archives/index.html

The Aeon Genesis translation is available from:
https://agtp.romhack.net/project.php?id=cavestory

To build the debugging symbols use:
  DEBUG=1 ./nxengine-libretro.SlackBuild