Swift 5.7 build errors

[rgoldberg]

Various commits broke the Swift 5.7 build:

Commit 83c5134a242086c053261095937f9964301a453a

• Package.swift: target array missing a comma
• ToolInfo.swift: adds 2 if expressions, which are not supported by Swift 5.7
• DumpHelpGenerationTests.swift: adds switch expression, which is not supported by Swift 5.7

Commit 44dd206a8528abde66dc52cd6e61f2991949b5a4:

• GenerateManual.swift: adds switch expression, which is not supported by Swift 5.7

ArgumentParser version:
main branch

Swift version:
swift-driver version: 1.62.15 Apple Swift version 5.7.2 (swiftlang-5.7.2.135.5 clang-1400.0.29.51)
Target: x86_64-apple-macosx12.0

Checklist

• If possible, I've reproduced the issue using the main branch of this package
• I've searched for existing GitHub issues

Steps to Reproduce

Attempt to build Swift Argument Parser main branch using compiler limited to Swift 5.7.

Expected behavior

Swift Argument Parser builds properly.

Actual behavior

Build errors.