Someone probably forgot to guard code referring to XInput stuff.

In file included from /usr/include/c++/12/memory:76,
                 from /home/jblackquill/KDE/Sources/kwin/src/core/platform.h:19,
                 from /home/jblackquill/KDE/Sources/kwin/src/backends/x11/standalone/x11_standalone_platform.h:11,
                 from /home/jblackquill/KDE/Sources/kwin/src/backends/x11/standalone/x11_standalone_platform.cpp:9:
/usr/include/c++/12/bits/unique_ptr.h: In instantiation of ‘void std::default_delete<_Tp>::operator()(_Tp*) const [with _Tp = KWin::XInputIntegration]’:
/usr/include/c++/12/bits/unique_ptr.h:396:17:   required from ‘std::unique_ptr<_Tp, _Dp>::~unique_ptr() [with _Tp = KWin::XInputIntegration; _Dp = std::default_delete<KWin::XInputIntegration>]’
/home/jblackquill/KDE/Sources/kwin/src/backends/x11/standalone/x11_standalone_platform.cpp:108:50:   required from here
/usr/include/c++/12/bits/unique_ptr.h:93:23: error: invalid application of ‘sizeof’ to incomplete type ‘KWin::XInputIntegration’
   93 |         static_assert(sizeof(_Tp)>0,
      |