libobs: Fix underlinking by adding libx11

We directly depend on libx11 for various operations in obs-nix-x11.c,
not just xcb. So be sure to link it in too.

fixes #11667

libobs/cmake/os-linux.cmake

@@ -47,6 +47,7 @@ endif()
 target_link_libraries(
   libobs
   PRIVATE
+    X11::X11
     X11::x11-xcb
     xcb::xcb
     LibUUID::LibUUID