Links Qt6 WebSockets in httq when module is real

qt6-after/qt6-migrated-legatus/Lts/Common/httq/CMakeLists.txt

@@ -1,8 +1,16 @@
 # Modified CMakeLists.txt from github.com/wille-io/httq
 
 # Make ${Qt6_WebSockets} optional
-if(QT6_GUI_AVAILABLE AND TARGET Qt6::WebSockets)
-  set(Qt6_WebSockets ${Qt6_WebSockets})
+# Link the real WebSockets module whenever the websocket code path is
+# compiled: QT6_WEBSOCKETS_AVAILABLE (root CMakeLists) and the manual
+# Qt6::WebSockets import are set when the real module was found. The old
+# QT6_GUI_AVAILABLE condition never held in this environment (Qt6
+# discovery takes the minimal path) and the Qt6_WebSockets variable was
+# never defined, so AbstractServer.cpp compiled the websocket code
+# without the module on the link line (undefined reference to
+# QWebSocketServer::handleConnection).
+if(QT6_WEBSOCKETS_REAL_FOUND OR Qt6WebSockets_FOUND)
+  set(Qt6_WebSockets Qt6::WebSockets)
 else()
   set(Qt6_WebSockets "")
 endif()