Use case

Hey there 👋 , I'm a maintainer at FlutterFire. We're looking to pass a build flag to the xcodebuild command ran when building a macOS app. We have an keychain issue on our CI that could possibly be resolved by passing in the --allowProvisioningUpdates build flag which you can read in the logs for the failed CI run here.

I found that it is possible to pass a key/value to the build here. The problem is, we would like to pass a build flag which isn't possible with the current setup as implemented here.

Proposal

I propose updating this implementation. It could, perhaps, look for an environment variable with the signature: FLUTTER_XCODE_FLAG_*.

For illustration, I could export FLUTTER_XCODE_FLAG_provisioning_profile=--allowProvisioningUpdates as an environment variable. The updated implementation would find keys that match on FLUTTER_XCODE_FLAG_ and take whatever value it has and pass it to xcodebuild as a flag rather than a key/value pair.

Hopefully, that makes sense. Let me know if you have any questions! Thanks 🙏.