[darwin] `fyne release` doesn't build universal macOS bundles

[pneumaticdeath]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

Building a .pkg app using the fyne cli fyne release ... doesn't build a universal binary, which is required to target systems older than MacOS 12.0, and fyne hard-codes the minimum MacOS version at 10.9.

How to reproduce

First I build a pacage with fyne release:

mitch@diemos KarmaManager % fyne release --target darwin \
    --certificate "${MACOSAPPSTORECERT}" \
    --profile "${MACOSAPPSTOREPROF}" \
    --category games

Then I try to upload it to apple

mitch@diemos KarmaManager % xcrun altool --upload-app -f KarmaManager.pkg -t macos -u "${IOSUPLOADUSER}" -p "${IOSUPLOADPASS}"
Running altool at path '/Applications/Xcode.app/Contents/SharedFrameworks/ContentDelivery.framework/Resources/altool'...

2026-04-03 14:35:20.552 ERROR: [ContentDelivery.Uploader.100F87090]
=======================================
UPLOAD FAILED with 1 error
=======================================
Failed to upload package.
2026-04-03 14:35:20.553 ERROR: [altool.100F87090] Validation failed (409) Invalid bundle. The “KarmaManager.app” bundle supports arm64 but not Intel-based Mac computers. Your build must include the x86_64 architecture to support Intel-based Mac computers. To support arm64 only, your macOS deployment target must be 12.0 or higher. For details, view: https://developer.apple.com/documentation/xcode/building_a_universal_macos_binary. (ID: ad39c682-a70a-416d-a745-f0be50c0256d)
   NSUnderlyingError : Validation failed (-19241) Invalid bundle. The “KarmaManager.app” bundle supports arm64 but not Intel-based Mac computers. Your build must include the x86_64 architecture to support Intel-based Mac computers. To support arm64 only, your macOS deployment target must be 12.0 or higher. For details, view: https://developer.apple.com/documentation/xcode/building_a_universal_macos_binary.
      status : 409
      detail : Invalid bundle. The “KarmaManager.app” bundle supports arm64 but not Intel-based Mac computers. Your build must include the x86_64 architecture to support Intel-based Mac computers. To support arm64 only, your macOS deployment target must be 12.0 or higher. For details, view: https://developer.apple.com/documentation/xcode/building_a_universal_macos_binary.
      id : ad39c682-a70a-416d-a745-f0be50c0256d
      code : STATE_ERROR.VALIDATION_ERROR
      title : Validation failed
   iris-code : STATE_ERROR.VALIDATION_ERROR

Screenshots

No response

Example code

Pretty much any MacOS build should exhibit this behavior.

Fyne version

fyne cli version: v1.7.0 fyne library version: v2.7.2

Go compiler version

1.25.2

Operating system and version

MacOS Tahoe 26.3.1

Additional Information

No response