fix: Use PosixPath, not NativePath, for Zip file archive members

The root of an archive is `/`, not a drive letter. So while `NativePath` works
here on POSIX, it will not make sense on Windows.

source/dub/packagemanager.d

@@ -891,11 +891,11 @@ class PackageManager {
 		logDebug("Extracting from zip.");
 
 		// In a GitHub zip, the actual contents are in a sub-folder
-		alias PSegment = typeof(NativePath.init.head);
+		alias PSegment = typeof(PosixPath.init.head);
 		PSegment[] zip_prefix;
 		outer: foreach(ArchiveMember am; archive.directory) {
             try {
-                auto path = NativePath(am.name).bySegment.array;
+                auto path = PosixPath(am.name).bySegment.array;
                 foreach (fil; packageInfoFiles)
                     if (path.length == 2 && path[$-1].name == fil.filename) {
                         zip_prefix = path[0 .. $-1];