When waiting for build script, use WaitForExitAsync.Wait instead of WaitForExit

Author: ktwrd

BuildService.Shared/Build/BuildInstance.cs

@@ -170,7 +170,7 @@ private void startThread(EventWaitHandle waitHandle)
             ScriptProcess.BeginOutputReadLine();
             ScriptProcess.BeginErrorReadLine();
 
-            ScriptProcess.WaitForExit();
+            ScriptProcess.WaitForExitAsync().Wait();
 
             Status = BuildStatus.Done;
             TargetItem.CurrentBuildStatus = Status;