Tiny debugger tests

* Ignoring the EventSets test because it tests exceptions.
* Fixing the vm.Exit() path that doesn't use System.Environment.Exit().

Author: Brian Raderman

mono/mini/debugger-agent.c

@@ -8750,11 +8750,11 @@ vm_commands (int command, int id, guint8 *p, guint8 *end, Buffer *buf)
 			while (suspend_count > 0)
 				resume_vm ();
 
+			mono_environment_exitcode_set (exit_code);
+			
 			if (!mono_runtime_try_shutdown ())
 				break;
 
-			mono_environment_exitcode_set (exit_code);
-
 			/* Suspend all managed threads since the runtime is going away */
 			DEBUG_PRINTF (1, "Suspending all threads...\n");
 			mono_thread_suspend_all_other_threads ();

mono/mini/il2cpp-stubs.cpp

@@ -900,7 +900,7 @@ gint32 il2cpp_mono_environment_exitcode_get()
 
 void il2cpp_mono_environment_exitcode_set(gint32 value)
 {
-	IL2CPP_ASSERT(0 && "This method is not yet implemented");
+    il2cpp::vm::Runtime::SetExitCode(value);
 }
 
 void il2cpp_mono_threadpool_suspend()