cmake: Move USED_OSG_(COMPONENTS|PLUGINS) before add_subdirectory(extern)

CMakeLists.txt

@@ -169,6 +169,26 @@ if (USE_QT)
     #set(CMAKE_AUTOMOC ON)
 endif()
 
+set(USED_OSG_COMPONENTS
+    osgDB
+    osgViewer
+    osgText
+    osgGA
+    osgParticle
+    osgUtil
+    osgFX
+    osgShadow
+    osgAnimation)
+set(USED_OSG_PLUGINS
+    osgdb_bmp
+    osgdb_dds
+    osgdb_freetype
+    osgdb_jpeg
+    osgdb_osg
+    osgdb_png
+    osgdb_serializers_osg
+    osgdb_tga)
+
 add_subdirectory(extern)
 
 # Sound setup
@@ -273,25 +293,6 @@ if(NOT HAVE_STDINT_H)
     message(FATAL_ERROR "stdint.h was not found" )
 endif()
 
-set(USED_OSG_COMPONENTS
-    osgDB
-    osgViewer
-    osgText
-    osgGA
-    osgParticle
-    osgUtil
-    osgFX
-    osgShadow
-    osgAnimation)
-set(USED_OSG_PLUGINS
-    osgdb_bmp
-    osgdb_dds
-    osgdb_freetype
-    osgdb_jpeg
-    osgdb_osg
-    osgdb_png
-    osgdb_serializers_osg
-    osgdb_tga)
 if(OPENMW_USE_SYSTEM_OSG)
     find_package(OpenSceneGraph 3.3.4 REQUIRED ${USED_OSG_COMPONENTS})
     if(OSG_STATIC)