[ALOY-1485] Warning on relocation of platform folder confusing if it contains only one platform

Take the following scenario:

I have an Alloy app that targets iOS and Android but only has a /platform/android, no /platform/ios.

I upgraden from Alloy 1.7.35 to 1.8.0, which includes ALOY-1365.

I continue to work on the iOS version of my app and get a warning to add /platform to my .gitignore file. Weird, because

why would I stop versioning that if it contains important stuff for Android?

After a while I switch to work on the Android version and it says:

[ERROR] Detected legacy "/platform" directory in project directory.
[ERROR] Please move the "/platform" directory to "/app/platform" for Alloy 1.8.0 or later.
[ERROR] Alloy compiler failed

This is confusing because didn't I work on my iOS app successfully using Alloy 1.8.0 without having moved the folder? Also, when I'd now move /i18n to /app/i18n as it suggests it would now also include an ios folder which contains a alloy_generated file. I think it would be better to do the check (and have the alloy_generated file in the root of /platform and not in the platform folders. It would then: * Already have failed to build when I started working on IOS after the upgrade. * The warning would not be confusing since it would only show on the second build after dealing with... * The error would not be confusing since it is about the root folder and not the platform one. * The /platform/ios would not have been generated, easing the relocation.