Fix build for -no-feature-textcodec

Change-Id: I98ef516031e8057456d8dab6de01576d2734d8f5
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

src/src.pro

 TEMPLATE = subdirs
 CONFIG += ordered
 
-SUBDIRS += websockets
-qtHaveModule(quick): SUBDIRS += imports
+qtConfig(textcodec) {
+    SUBDIRS += websockets
+    qtHaveModule(quick): SUBDIRS += imports
+}