Debugger: Remove non-const access to RunParameters

The idea is that they shouldn't change after start() to
be re-usable for an additional run later.

Change-Id: I272fc975657b0d8b5b13a07d58bd0b626868d32e
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/debuggerruncontrol.cpp

@@ -728,6 +728,12 @@ bool DebuggerRunTool::fixupParameters()
         rp.useTerminal = false;
     }
 
+    if (rp.isNativeMixedDebugging())
+        rp.inferior.environment.set("QV4_FORCE_INTERPRETER", "1");
+
+    if (rp.isCppDebugging && !rp.skipExecutableValidation)
+        rp.validateExecutable();
+
     return true;
 }