Application is rebuilt when passing --env.uglify for a first time

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: 5.2.0
• Android Runtime: 5.2.0
• iOS Runtime: 5.2.0

Describe the bug
when you run project with: tns run ios --bundle and then with: tns run ios --bundle --env.uglify, you will see that the project will pass through building process.

To Reproduce

1. tns create appNG --ng
2. tns run ios --bundle
3. stop the process
4. tns run ios --bundle --env.uglify
   you will see : Building project..., Project successfully built. in console logs

Expected behavior
not sure this behavior is correct

先重現 issue 中的兩個命令：tns run ios --bundle，接著是 tns run ios --bundle --env.uglify，並比較建置日誌。閱讀 NativeScript CLI 的建置與打包進入點，以判斷變更 --env.uglify 是否應該使現有建置失效；當行為和預期結果已完成文件化，並由回歸測試涵蓋時，即表示完成。