build: complete the changes from #423 (#425)
build: complete the changes from #423 (#425)

This adds `-parse-as-library` to the example targets which use `@main`
resulting in a compile failure as `@main` is not processed unless the
target is marked as library.

Authored-by: Saleem Abdulrasool <d3629432f14a71b62e796d32d075121c69cf67de@compnerd.org>
apple/swift-argument-parser,apple/swift-argument-parser