Utils: Fix (Q)Process::interrupt

Since switching to a QProcess based implementation a different
code path is used to interrupt processes (QProcessImpl::sendControlSignal, instead of ProcessLauncherImpl::sendControlSignal).

The QProcess path still used outdated ProcessHelper::interruptProcess.

This patch removes the old path and replaces it with the correct
"ProcessHelper::interruptPid" for QProcess based processes.

This also fixes GdbEngine::interruptInferior2 which could not interrupt
processes during "Attach to running server"

Change-Id: I9e1917100acf89c07cab0d9c687e57bb555d9d83
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/process.cpp

@@ -486,7 +486,7 @@ private:
             m_process->kill();
             break;
         case ControlSignal::Interrupt:
-            ProcessHelper::interruptProcess(m_process);
+            ProcessHelper::interruptPid(m_process->processId());
             break;
         case ControlSignal::KickOff:
             QTC_CHECK(false);

src/libs/utils/processutils.cpp

@@ -180,11 +180,4 @@ void ProcessHelper::interruptPid(qint64 pid)
 #endif
 }
 
-void ProcessHelper::interruptProcess(QProcess *process)
-{
-    ProcessHelper *helper = qobject_cast<ProcessHelper *>(process);
-    if (helper && helper->m_useCtrlCStub)
-        ProcessHelper::interruptPid(process->processId());
-}
-
 } // namespace Utils

src/libs/utils/processutils.h

@@ -45,7 +45,6 @@ public:
     void setUseCtrlCStub(bool enabled); // release only
 
     static void terminateProcess(QProcess *process);
-    static void interruptProcess(QProcess *process);
     static void interruptPid(qint64 pid);
 
 private: