Since commit 2073b55, Guix uses CPLUS_INCLUDE_PATH to find system
headers. Overriding this variable caused a compile failure. The package builds
fine without it, so just drop it.
* nongnu/packages/game-development.scm (eduke32)[arguments]: Drop ‘set-sdl-paths’ phase.
Signed-off-by: Jonathan Brielmaier <jonathan.brielmaier@web.de>