docs(upgrade): correctly document how to use AOT compilation for hybrid apps #35989
Description
📚 Docs or angular.io bug report
Description
The ngUpgrade guide uses the old SystemJS-based setup (i.e. not using @angular/cli). It has a section about using Ahead-of-Time (AOT) compilation.
In the latest docs, that section points to the AOT guide. However, the guide has been updated to assume a CLI-based app and is therefore not applicable to the SystemJS-based apps used in the ngUpgrade guide.
The latest version of the AOT guide that assumes a SystemJS-based app is on v4. Even that version of the guide, however, seems to not work as described for v9+ Ivy apps.
The AOT section has been removed from the ngUpgrade guide in #34374 to avoid confusion.
We need to re-introduce a working version of it. Either provide correct instructions on how to use AOT compilation in SystemJS-based v9+ Ivy apps or (better yet) update the ngUpgrade guides to use hybrid apps based on @angular-cli (which is a bigger effort).