Document Xcode Cordova build pitfall

[brody4hire]

Coming from the symptom from https://github.com/apache/cordova-ios/issues/760#issuecomment-645604332:

I get the same error.

with explanation of the pitfall from https://github.com/apache/cordova-ios/issues/760#issuecomment-645616290:

it looks like your Xcode GUI is trying to just build the Cordova subproject, which is not really tested or supported by us. Please click on this control and use it to select your application build project:

I suspect that this would affect other users. I think this should be documented as a pitfall.

The screenshots may be outdated but I think the pitfall is self-evident and needs to be documented. I think this is not specific to Ionic.

[Rahulbhutani97]

Build succeded :: in VScode

When i open .xcodeProj file then run build it shows error of info.plist