Debugger: Fix "Restart debugging session" regression

Introduced with the support for fork-follows-child.
With 'Restart', we temporarily don't have a living
thread, so that can't be taken as indication for
ending the debugging session.

Task-number: QTCREATORBUG-14393
Change-Id: I0070b9ca7e6897dab48bdbcf493d03df4709be98
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>

src/plugins/debugger/gdb/gdbengine.cpp

@@ -240,6 +240,7 @@ GdbEngine::GdbEngine(const DebuggerRunParameters &startParameters)
     m_terminalTrap = startParameters.useTerminal;
     m_fullStartDone = false;
     m_systemDumpersLoaded = false;
+    m_rerunPending = true;
 
     m_debugInfoTaskHandler = new DebugInfoTaskHandler(this);
     //ExtensionSystem::PluginManager::addObject(m_debugInfoTaskHandler);
@@ -1972,9 +1973,13 @@ void GdbEngine::handleThreadGroupCreated(const GdbMi &result)
 void GdbEngine::handleThreadGroupExited(const GdbMi &result)
 {
     QByteArray groupId = result["id"].data();
-    if (threadsHandler()->notifyGroupExited(groupId))
+    if (threadsHandler()->notifyGroupExited(groupId)) {
+        if (m_rerunPending)
+            m_rerunPending = false;
+        else
             notifyInferiorExited();
     }
+}
 
 int GdbEngine::currentFrame() const
 {
@@ -4322,6 +4327,7 @@ void GdbEngine::resetInferior()
             }
         }
     }
+    m_rerunPending = true;
     requestInterruptInferior();
     runEngine();
 }

src/plugins/debugger/gdb/gdbengine.h

@@ -211,6 +211,7 @@ private:
     CommandsDoneCallback m_commandsDoneCallback;
 
     QList<DebuggerCommand> m_commandsToRunOnTemporaryBreak;
+    bool m_rerunPending;
 
 private: ////////// Gdb Output, State & Capability Handling //////////
 protected: