Qt6: add d3d12 system lib on Windows

Qt 6.6.0 added `d3d12` to the list of system libraries on Windows it links against:
qt/qtbase@84fb0de#diff-2d8b127aed7a6123be24b80481b760ec4e9cc251e19d668d936dc09e87147a0e

This is currently breaking the build in #18794.

recipes/qt/6.x.x/conanfile.py

@@ -1039,7 +1039,7 @@ def _create_plugin(pluginname, libname, plugintype, requires):
 
             if self.settings.os == "Windows":
                 self.cpp_info.components["qtGui"].system_libs = ["advapi32", "gdi32", "ole32", "shell32", "user32", "d3d11",
-                    "dxgi", "dxguid", "d2d1", "dwrite", "d3d9", "setupapi", "SHCore"]
+                    "dxgi", "dxguid", "d2d1", "dwrite", "d3d9", "setupapi", "SHCore", "d3d12"]
                 if self.settings.compiler == "gcc":
                     self.cpp_info.components["qtGui"].system_libs.append("uuid")
                 _create_plugin("QWindowsIntegrationPlugin", "qwindows", "platforms", ["Core", "Gui"])