If I tried to export an .ipa from an .xcarchive using the command line using xcodebuild as such:
xcodebuild archive -scheme "Cross" -archivePath "build/Cross.xcarchive"
xcodebuild -exportArchive -archivePath "build/Cross.xcarchive" -exportPath "build/Cross-tvOS.ipa"
it fails with the error "the platform is unknown: appletvos":
+ xcodebuild -exportArchive -archivePath build/Cross.xcarchive -exportFormat app -exportPath build/Cross-tvOS.ipa
--- xcodebuild: WARNING: -exportArchive without -exportOptionsPlist is deprecated
2015-11-30 22:13:44.403 xcodebuild[42874:30912505] [MT] DVTAssertions: Warning in /Library/Caches/com.apple.xbs/Sources/IDEFrameworks/IDEFrameworks-9081/IDEFoundation/Execution/Archiving/IDEArchivedApplication.m:148
Details: Asked if we support packaging as a given format, but the platform is unknown: appletvos
Object: <IDEArchivedApplication: 0x7f89bea3e990>
Method: -supportsPackagingAsFormat:
Thread: <NSThread: 0x7f89bbc320d0>{number = 1, name = main}
Please file a bug at http://bugreport.apple.com with this warning message and any useful information you can provide.
error: archive at path '/Users/pol/Downloads/Cross/tvOS/build/Cross.xcarchive' cannot be exported as APP
** EXPORT FAILED **
I can successfully export the .ipa using the Xcode Organizer. This was observed on Xcode version 7.1.1.
It turns out the error message is misleading. This failure happens if you don't specify the -exportOptionsPlist argument.
Even passing a fake empty .plist file like this fixes the issue:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict/>
</plist>