(iOS)(add-to-app): SWIFT_VERSION missing when compiling the iOS app

[martin-headspace]

Expected Behavior

On an add-to-app build, the app using this plugin should compile successfully and without a hitch.

Current Behavior

Developers get the following error:

- amplitude_flutter does not specify a Swift version and none of the targets (Runner) integrating it have the SWIFT_VERSION attribute set. Please contact the author or set the SWIFT_VERSION attribute in at least one of the targets that integrate this pod.

Developers can fix this by setting the SWIFT_VERSION environment variable to Swift 5.0 or above.

ENV['SWIFT_VERSION'] = '5'

Which, on most Flutter apps is a one time fix, but add-to-app developers have to either set this environment variable on their generated projects every time they compile OR they have to set it elsewhere that can be accessed.

Possible Solution

#210

Steps to Reproduce

1. Create or reuse an existing add-to-app Flutter module.
2. Try to compile for an iOS Device.
3. Voila

Environment

• SDK Version: Latest
• Flutter Version: Latest Stable
• Device: All iOS
• Device OS and Version: Any iOS