`tns prepare ios --watch` does not "watch" the project/node_modules for changes

Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 6.0.2
• Cross-platform modules:
• Android Runtime:
• iOS Runtime:
• Plugin(s):

Describe the bug
Executing tns prepare ios --watch on a project compatible with 6.0.0, the project is correctly prepared but it is not being watched and making any changes to the app or node_modules folders does not trigger new prepare.

To Reproduce

• Make a new app using CLI
• Run `tns prepare ios --watch
• Wait for the project to prepare
• Make changes to the app folder or any nativescript plugin in node_modules
• The app is not re-prepared

Expected behavior
Using --watch watches the app and node_modules for changes

先在新的 CLI 相容應用程式中執行 tns prepare ios --watch，並觀察 app 和 node_modules 目錄下的變更是否會觸發再次 prepare。追蹤 prepare ios 的 watch 進入點及其檔案監看設定；當兩個位置都能可靠地觸發重新 prepare 時即表示完成。