x11-wm/hyprland: unbreak with global X11=off (OPTIONS_UNSET=X11)

In file included from ../src/layout/../defines.hpp:1,

from ../src/layout/IHyprLayout.hpp:3,
from ../src/layout/IHyprLayout.cpp:1:

../src/layout/../includes.hpp:9:10: fatal error: X11/Xlib.h: No such file or directory

9 | #include <X11/Xlib.h>
  |          ^~~~~~~~~~~~