Fix the build for compilation error

cmd/oras/internal/option/packer.go

@@ -77,7 +77,7 @@ func (opts *Packer) Parse() error {
 	if !opts.PathValidationDisabled {
 		for _, path := range opts.FileRefs {
 			// Remove the type if specified in the path <file>[:<type>] format
-			path, _, err = fileref.Parse(path, "")
+			path, _, err := fileref.Parse(path, "")
 			if err != nil {
 				return err
 			}