Common/CMakeLists: Link in libraries privately for traversal_server

Without this, CMake script errors can occur, as explicit linkage
specifiers and non-explicit specifier commands aren't compatible with
one another.

Source/Core/Common/CMakeLists.txt

@@ -159,10 +159,10 @@ if(UNIX)
   add_executable(traversal_server TraversalServer.cpp)
   target_link_libraries(traversal_server PRIVATE common)
   if(SYSTEMD_FOUND)
-    target_link_libraries(traversal_server ${SYSTEMD_LIBRARIES})
+    target_link_libraries(traversal_server PRIVATE ${SYSTEMD_LIBRARIES})
   endif()
   if(HAIKU)
-    target_link_libraries(traversal_server network)
+    target_link_libraries(traversal_server PRIVATE network)
   endif()
 elseif(WIN32)
   target_link_libraries(common PRIVATE "-INCLUDE:enableCompatPatches")