CMake: Find more external libraries

Check for LibNotify, MSpack, XTest and GnomeVFS2.

build/cmake/lib/core/CMakeLists.txt

@@ -86,5 +86,9 @@ if(UNIX AND wxUSE_LIBSDL)
         wx_lib_link_libraries(core PUBLIC ${SDL_LIBRARY})
     endif()
 endif()
+if(wxUSE_LIBNOTIFY)
+    wx_lib_include_directories(core PUBLIC ${LIBNOTIFY_INCLUDE_DIRS})
+    wx_lib_link_libraries(core PUBLIC ${LIBNOTIFY_LIBRARIES})
+endif()
 
 wx_finalize_lib(core)