Address PR feeback

Author: MaxDesiatov

Sources/Basics/Archiver/UniversalArchiver.swift

@@ -15,7 +15,7 @@ import protocol TSCBasic.FileSystem
 
 /// An `Archiver` that handles multiple formats by delegating to other existing archivers each dedicated to its own
 /// format.
-public final class UniversalArchiver: Archiver {
+public struct UniversalArchiver: Archiver {
     public var supportedExtensions: Set<String>
 
     /// Errors specific to the implementation of ``UniversalArchiver``.

Sources/Basics/Archiver/ZipArchiver.swift

@@ -14,7 +14,7 @@ import TSCBasic
 import Dispatch
 
 /// An `Archiver` that handles ZIP archives using the command-line `zip` and `unzip` tools.
-public final class ZipArchiver: Archiver, Cancellable {
+public struct ZipArchiver: Archiver, Cancellable {
     public var supportedExtensions: Set<String> { ["zip"] }
 
     /// The file-system implementation used for various file-system operations and checks.