Cygwin: pty: Call FreeConsole() only if attached to current pty.

- After commit 071b8e0cbd, the problem
  reported in https://cygwin.com/pipermail/cygwin/2020-May/244873.html
  occurs. This is due to freeing console device accidentally rather
  than pseudo console. This patch makes sure to call FreeConsole()
  only if the process is attached to the pseudo console of the current
  pty.

winsup/cygwin/fhandler.h

@@ -2284,6 +2284,7 @@ class fhandler_pty_slave: public fhandler_pty_common
 
   bool try_reattach_pcon ();
   void restore_reattach_pcon ();
+  inline void free_attached_console ();
 
  public:
   /* Constructor */

winsup/cygwin/fhandler_tty.cc

@@ -180,6 +180,16 @@ set_ishybrid_and_switch_to_pcon (HANDLE h)
     }
 }
 
+inline void
+fhandler_pty_slave::free_attached_console ()
+{
+  if (freeconsole_on_close && get_minor () == pcon_attached_to)
+    {
+      FreeConsole ();
+      pcon_attached_to = -1;
+    }
+}
+
 #define DEF_HOOK(name) static __typeof__ (name) *name##_Orig
 DEF_HOOK (WriteFile);
 DEF_HOOK (WriteConsoleA);
@@ -708,11 +718,7 @@ fhandler_pty_slave::~fhandler_pty_slave ()
   if (!get_ttyp ())
     {
       /* Why comes here? Who clears _tc? */
-      if (freeconsole_on_close)
-	{
-	  FreeConsole ();
-	  pcon_attached_to = -1;
-	}
+      free_attached_console ();
       return;
     }
   if (get_pseudo_console ())
@@ -739,11 +745,7 @@ fhandler_pty_slave::~fhandler_pty_slave ()
       if (used == 0)
 	{
 	  init_console_handler (false);
-	  if (freeconsole_on_close)
-	    {
-	      FreeConsole ();
-	      pcon_attached_to = -1;
-	    }
+	  free_attached_console ();
 	}
     }
 }
@@ -3006,11 +3008,7 @@ fhandler_pty_slave::fixup_after_exec ()
       if (used == 1 /* About to close this tty */)
 	{
 	  init_console_handler (false);
-	  if (freeconsole_on_close)
-	    {
-	      FreeConsole ();
-	      pcon_attached_to = -1;
-	    }
+	  free_attached_console ();
 	}
     }