Add flags to Swift Packages

[uhooi]

Overview

Give the following Other Swift Flags to Swift Packages:

• -warn-long-expression-type-checking=500
• -warn-long-function-bodies=500
• -warn-concurrency
• -enable-actor-data-race-checks

References

• https://twitter.com/the_uhooi/status/1482624317586219009?s=20
• https://forums.swift.org/t/can-xfrontend-enable-experimental-concurrency-be-enabled-in-a-package/42805
• https://github.com/apple/swift-evolution/blob/main/proposals/0238-package-manager-build-settings.md
• https://developer.apple.com/documentation/swift_packages/swiftsetting/3112770-unsafeflags
• https://developer.apple.com/documentation/swift_packages/buildsettingcondition

[github-actions[bot]]

👋 Thanks for reporting! Please PR :)