Utils: Don't raise SIGSTOP in the process stub

Previously, the starting inferior was sent a SIGSTOP to avoid
progress before the debugger could attach.

However, these signals are then also visible in the debugger and
need to be ignored as part of the startup handling in Creator.

The waiting effect can be achieved less intrusively by waiting
on a pipe read between fork() and exec().

Task-number: QTCREATORBUG-25073
Task-number: QTCREATORBUG-25082
Task-number: QTCREATORBUG-25227
Change-Id: Ie70b9eb5ea865f85411c26b0dbf377a019fec8d5
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/terminal.cpp

@@ -183,6 +183,11 @@ TerminalRunner::TerminalRunner(RunControl *runControl, const Runnable &stubRunna
             this, [this] { reportDone(); });
 }
 
+void TerminalRunner::kickoffProcess()
+{
+    m_stubProc.kickoffProcess();
+}
+
 void TerminalRunner::interruptProcess()
 {
     m_stubProc.interruptProcess();