Merge branch 'OSG_check_cmake' into 'master'

cmake check to enforce that if someone uses OSG 3.6, that it is at least 3.6.5

See merge request OpenMW/openmw!941

CMakeLists.txt

@@ -355,7 +355,11 @@ if(NOT HAVE_STDINT_H)
 endif()
 
 if(OPENMW_USE_SYSTEM_OSG)
-    find_package(OpenSceneGraph 3.3.4 REQUIRED ${USED_OSG_COMPONENTS})
+    find_package(OpenSceneGraph 3.4.0 REQUIRED ${USED_OSG_COMPONENTS})
+    if (${OPENSCENEGRAPH_VERSION} VERSION_GREATER 3.6.2 AND ${OPENSCENEGRAPH_VERSION} VERSION_LESS 3.6.5)
+        message(FATAL_ERROR "OpenSceneGraph version ${OPENSCENEGRAPH_VERSION} has critical regressions which cause crashes. Please upgrade to 3.6.5 or later. We strongly recommend using the tip of the official 'OpenSceneGraph-3.6' branch or the tip of '3.6' OpenMW/osg (OSGoS).")
+    endif()
+
     if(OSG_STATIC)
         find_package(OSGPlugins REQUIRED COMPONENTS ${USED_OSG_PLUGINS})
     endif()