rewrite swiftSettings to avoid causing SPM build failures

[tayloraswift]

fixes the issue described here by kicking the unsafe flags logic up a level, so non-CI builds pass an empty array of SwiftSettings instead of an empty array of unsafe flags.

[ahoppen]

Thanks for fixing this. For readability, however, I would prefer to use an if instead the map, and just change `swiftSyntaxUnsafeSwiftFlags

var swiftSyntaxSwiftSettings: [SwiftSetting] = []

/// If we are in a controlled CI environment, we can use internal compiler flags
/// to speed up the build or improve it.
if ProcessInfo.processInfo.environment["SWIFT_BUILD_SCRIPT_ENVIRONMENT"] != nil {
  let groupFile = URL(fileURLWithPath: #file)
    .deletingLastPathComponent()
    .appendingPathComponent("utils")
    .appendingPathComponent("group.json")

  swiftSyntaxSwiftSettings.append(.unsafeFlags([
    "-Xfrontend", "-group-info-path",
    "-Xfrontend", groupFile.path,
    // Enforcing exclusivity increases compile time of release builds by 2 minutes.
    // Disable it when we're in a controlled CI environment.
    "-enforce-exclusivity=unchecked"
  ]))
}

[tayloraswift]

rewrote it without the map, is

if case _? = ProcessInfo.processInfo.environment["SWIFT_BUILD_SCRIPT_ENVIRONMENT"] {

fine?

[ahoppen]

Thanks for continuing to drive this. I’ve got two more stylistic comments inline.

[ahoppen]

Thanks. Looks good to me now.

[ahoppen]

@swift-ci Please test

[tayloraswift]

is this ready to merge?

[ahoppen]

Sorry, forgot to hit the merge button. Thanks for the ping.