Catch Xcode 8.3 legacy API while patching Xcode PackageApplication script

[KrauseFx]

• This will show an appropriate error message for Xcode 8.3 users that still have the legacy build API enabled. We want to migrate 100% of the users away from it, as it was now officially removed from Xcode
• Also link to the release that contains the migration information

[fastlane-bot]

Hey @KrauseFx 👋

Thank you for your contribution to fastlane and congrats on getting this pull request merged 🎉
The code change now lives in the master branch, however it wasn't released to RubyGems yet.
We usually ship about once a week, and your PR will be included in the next one.

Please let us know if this change requires an immediate release by adding a comment here 👍
We'll notify you once we shipped a new release with your changes 🚀

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.25.0 🚀

[ChrisAJS]

Any clarification on what 'export_type' is? As referenced here

[KrauseFx]

    def self.legacy_api_note!
      UI.important "Unfortunately the legacy build API was removed with Xcode 8.3."
      UI.important "Please make sure to remove use_legacy_build_api from your ./fastlane/Fastfile"
      UI.important "and update the gym call to include the export method like this:"
      UI.important "== App Store Builds =="
      UI.error '     gym(scheme: "MyScheme", export_method: "app-store")'
      UI.important "==  Ad Hoc Builds =="
      UI.error '     gym(scheme: "MyScheme", export_method: "ad-hoc")'
      UI.important "== Development Builds =="
      UI.error '     gym(scheme: "MyScheme", export_method: "development")'
      UI.important "== In-House Enterprise Builds =="
      UI.error '     gym(scheme: "MyScheme", export_method: "enterprise")'
      UI.important "If you run into a code signing error, please check out our troubleshooting guide for more information on how to solve the most common issues"
      UI.error "    https://docs.fastlane.tools/codesigning/troubleshooting/ 🚀"
      UI.important ""
      UI.user_error! "legacy_build_api removed!"
    end