Replace -x with -- for gnome-terminal

-x is deprecated.

Change-Id: Ic00b8042caff1620abe3e51f9d3b3198d606f084
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/consoleprocess_unix.cpp

@@ -353,7 +353,7 @@ static const Terminal knownTerminals[] =
     {"urxvt", "-e"},
     {"xfce4-terminal", "-x"},
     {"konsole", "-e"},
-    {"gnome-terminal", "-x"}
+    {"gnome-terminal", "--"}
 };
 
 QString ConsoleProcess::defaultTerminalEmulator()