package/ogre: remove libglu dependency

"The inclusion of GLU is historical. [...] I'd recommend using
 -DGLEW_NO_GLU since GLU is rarely seen in modern codebases nowadays."
https://github.com/nigels-com/glew/issues/192#issuecomment-411641657



Add -DGLEW_NO_GLU to get rid of the libglu dependency.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
[yann.morin.1998@free.fr:
  - fix mismatch between OGRE_CXX_FLAGS and OGRE_CXXFLAGS
  - also use OGRE_CFLAGS for symetry with OGRE_CXXFLAGS
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>