     }
 }
 
-public class ClangTarget: Target {
+public final class ClangTarget: Target {
 
     /// The default public include directory component.
     public static let defaultPublicHeadersComponent = "include"

    }
}

public class SwiftTarget: Target {

    /// The file name of linux main file.
    public static let linuxMainBasename = "LinuxMain.swift"

    }
}

public final class BinaryTarget: Target {

    /// The original source of the binary artifact.
    public enum ArtifactSource: Equatable, Codable {
