Added debugging mode for simultaneous QML and C++ debugging

It's not yet possible to attach to an external app running a qml
debugging server, because the server is only started on startup if an
env variable is set. Changing this requires action from Brisbane, but
even the current solution works for C++ apps with QML in them.

Task-number: BAUHAUS-585
Reviewed-by: dt

src/plugins/debugger/debuggerrunner.cpp

@@ -169,6 +169,11 @@ DebuggerRunControl::DebuggerRunControl(DebuggerManager *manager, const DebuggerS
     m_startParameters->useTerminal = false;
 }
 
+void DebuggerRunControl::setCustomEnvironment(ProjectExplorer::Environment env)
+{
+    m_startParameters->environment = env.toStringList();
+}
+
 void DebuggerRunControl::init()
 {
     connect(m_manager, SIGNAL(debuggingFinished()),