ci: make Windows render plugins entry-point-only (fix duplicate symbols)

oakengine-obj already contains openglrenderer.cpp and its moc output;
compiling them again into oakgl.dll plus embedding oakengine-obj caused
duplicate definitions and a stray k_app_version reference. On Windows
the plugins now compile only the C entry point and link oakengine-obj +
olive-version-obj.

engine/CMakeLists.txt

@@ -165,18 +165,23 @@ if (OAK_ENABLE_DYNAMIC_RENDER_BACKEND)
         endif ()
     endforeach ()
 
+    if (WIN32)
+        # Engine-internal C++ symbols are not exported from liboakengine.dll,
+        # so embed the object library like the engine tests do. oakengine-obj
+        # already contains openglrenderer.cpp and its moc output, so on
+        # Windows the plugin only needs the C entry point (duplicating the
+        # sources would cause duplicate definitions at link time). MinGW
+        # compares type_info by name, so cross-DLL RTTI still works.
+        add_library(oakgl SHARED render/opengl/openglbackend_c.cpp)
+        set_target_properties(oakgl PROPERTIES AUTOMOC OFF)
+        target_link_libraries(oakgl PRIVATE oakengine-obj
+                $<TARGET_OBJECTS:olive-version-obj>)
+    else ()
         add_library(oakgl SHARED
                 render/opengl/openglbackend_c.cpp
                 render/opengl/openglrenderer.cpp
                 render/opengl/openglrenderer.h
         )
-    if (WIN32)
-        # Engine-internal C++ symbols (olive::Renderer, FileFunctions, ...) are
-        # not exported from liboakengine.dll; embed the object library like the
-        # engine tests do. MinGW compares type_info by name, so cross-DLL RTTI
-        # with the shared engine still works.
-        target_link_libraries(oakgl PRIVATE oakengine-obj)
-    else ()
         target_link_libraries(oakgl PRIVATE oakengine)
     endif ()
     if (COMMAND oak_copy_otio_runtime)
@@ -200,15 +205,19 @@ if (OAK_ENABLE_DYNAMIC_RENDER_BACKEND)
     )
 
     if (Vulkan_FOUND)
+        if (WIN32)
+            # Same treatment as oakgl (see above): entry point only, engine
+            # objects come from oakengine-obj.
+            add_library(oakvulkan SHARED render/vulkan/vulkanbackend_c.cpp)
+            set_target_properties(oakvulkan PROPERTIES AUTOMOC OFF)
+            target_link_libraries(oakvulkan PRIVATE oakengine-obj
+                    $<TARGET_OBJECTS:olive-version-obj>)
+        else ()
             add_library(oakvulkan SHARED
                     render/vulkan/vulkanbackend_c.cpp
                     render/vulkan/vulkanrenderer.cpp
                     render/vulkan/vulkanrenderer.h
             )
-        if (WIN32)
-            # Same as oakgl: embed the engine objects on Windows (see above).
-            target_link_libraries(oakvulkan PRIVATE oakengine-obj)
-        else ()
             target_link_libraries(oakvulkan PRIVATE oakengine)
         endif ()
         if (COMMAND oak_copy_otio_runtime)