Debugger: Expand macros in "Additional Startup Commands"

Fixes: QTCREATORBUG-26382
Change-Id: I43cc2ac9451dbb44bcc12ed8555535fb8b4e437e
Reviewed-by: Artem Sokolovskii <artem.sokolovskii@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/debuggerengine.cpp

@@ -1891,7 +1891,7 @@ QString DebuggerEngine::nativeStartupCommands() const
         return !trimmed.isEmpty() && !trimmed.startsWith('#');
     });
 
-    return lines.join('\n');
+    return expand(lines.join('\n'));
 }
 
 Perspective *DebuggerEngine::perspective() const