`tns migrate` clears the platforms and next build fails if a custom android runtime was used

If tns migrate was ran on an app with a custom android runtime (tns platform add android --frameworkPath /test/runtime.tgz), next build would fail. This is because the platforms/android folder is deleted and the version of the tns-android package was previously set in the package.json to the literal next version of the runtime. This runtime, of course, couldn't be found in npm and thus the build fails. Couldn't runtimes added with --frameworkPath be handled differently and in some way marked as such in the package.json? Also, couldn't a simple gradlew clean do the dirty work instead of deleting the whole platforms folder?

首先追蹤 tns migrate 的進入點及其對 --frameworkPath 的處理，然後檢查 package.json 如何記錄 tns-android 的版本，以及如何移除 platforms/android。將該行為與提到的 gradlew clean 選項進行比較。當遷移使用自訂 runtime 的應用程式能保留可用的 runtime 參照，且下一次建置成功時，即表示完成。