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>

package/ogre/Config.in

@@ -10,7 +10,6 @@ config BR2_PACKAGE_OGRE
 	depends on BR2_USE_WCHAR # use wchar_t
 	select BR2_PACKAGE_FREETYPE
 	select BR2_PACKAGE_LIBFREEIMAGE
-	select BR2_PACKAGE_LIBGLU # GL/glu.h
 	select BR2_PACKAGE_SDL2
 	select BR2_PACKAGE_SDL2_OPENGL
 	select BR2_PACKAGE_SDL2_X11 # use wmInfo.info.x11

package/ogre/ogre.mk

@@ -15,7 +15,6 @@ OGRE_DEPENDENCIES = host-pkgconf \
 	freetype \
 	libfreeimage \
 	libgl \
-	libglu \
 	sdl2 \
 	xlib_libX11 \
 	xlib_libXaw \
@@ -23,12 +22,17 @@ OGRE_DEPENDENCIES = host-pkgconf \
 	xlib_libXrandr \
 	zziplib
 
+OGRE_CFLAGS = $(TARGET_CFLAGS) -DGLEW_NO_GLU
+OGRE_CXXFLAGS = $(TARGET_CXXFLAGS) -DGLEW_NO_GLU
+
 # Unbundle freetype and zziplib.
 # Disable java and nvidia cg support.
 OGRE_CONF_OPTS = -DOGRE_BUILD_DEPENDENCIES=OFF \
 	-DOGRE_BUILD_COMPONENT_JAVA=OFF \
 	-DOGRE_BUILD_PLUGIN_CG=OFF \
-	-DOGRE_INSTALL_DOCS=OFF
+	-DOGRE_INSTALL_DOCS=OFF \
+	-DCMAKE_C_FLAGS="$(OGRE_CFLAGS)" \
+	-DCMAKE_CXX_FLAGS="$(OGRE_CXXFLAGS)"
 
 # Enable optional python component if python interpreter is present on the target.
 ifeq ($(BR2_PACKAGE_PYTHON)$(BR2_PACKAGE_PYTHON3),y)
@@ -41,7 +45,7 @@ endif
 
 # Uses __atomic_fetch_add_8
 ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
-OGRE_CONF_OPTS += -DCMAKE_CXX_FLAGS="$(TARGET_CXXFLAGS) -latomic"
+OGRE_CXXFLAGS += -latomic
 endif
 
 $(eval $(cmake-package))