fix simulation build, missing glut library

Building on mac:

```
Undefined symbols for architecture x86_64:
  "_glutCreateWindow", referenced from:
      pcl::simulation::SimExample::initializeGL(int, char**) in simulation_io.cpp.o
  "_glutInit", referenced from:
      pcl::simulation::SimExample::initializeGL(int, char**) in simulation_io.cpp.o
  "_glutInitDisplayMode", referenced from:
      pcl::simulation::SimExample::initializeGL(int, char**) in simulation_io.cpp.o
  "_glutInitWindowPosition", referenced from:
      pcl::simulation::SimExample::initializeGL(int, char**) in simulation_io.cpp.o
  "_glutInitWindowSize", referenced from:
      pcl::simulation::SimExample::initializeGL(int, char**) in simulation_io.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [lib/libpcl_simulation_io.1.7.0.dylib] Error 1
make[1]: *** [simulation/tools/CMakeFiles/pcl_simulation_io.dir/all] Error 2
```