     }
 }
 
-public class SystemLibraryTarget: Target {
+public final class SystemLibraryTarget: Target {
 
     /// The name of pkgConfig file, if any.
     public let pkgConfig: String?

    }
}

public class SwiftTarget: Target {

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

    }
}

public final class ClangTarget: Target {

    /// The default public include directory component.
    public static let defaultPublicHeadersComponent = "include"
