[nix-shell:~/Code/cmaketest/build]$ make
[ 50%] Building CXX object CMakeFiles/osg-example.dir/main.cpp.o
In file included from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/GL2Extensions:27:0,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/Shader:25,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/StateAttribute:20,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/StateSet:18,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/Node:19,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/NodeVisitor:17,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osgGA/EventVisitor:17,
                 from /nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osgViewer/Viewer:18,
                 from /home/aaron/Code/cmaketest/main.cpp:2:
/nix/store/9zr7p1ihz955ipxy1qfpi6pnmw813wlk-openscenegraph-3.2.3/include/osg/GL:124:35: fatal error: GL/gl.h: No such file or directory
compilation terminated.
make[2]: *** [CMakeFiles/osg-example.dir/build.make:63: CMakeFiles/osg-example.dir/main.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:68: CMakeFiles/osg-example.dir/all] Error 2
make: *** [Makefile:84: all] Error 2