Fix Emacs style frozen string literal comment check

CHANGELOG.md

@@ -15,6 +15,7 @@
 * [#5538](https://github.com/rubocop-hq/rubocop/issues/5538): Fix false negatives in modifier cops when line length cop is disabled. ([@drenmi][])
 * [#6340](https://github.com/rubocop-hq/rubocop/pull/6340): Fix an error for `Rails/ReversibleMigration` when block argument is empty. ([@koic][])
 * [#6274](https://github.com/rubocop-hq/rubocop/issues/6274): Fix "[Corrected]" message being displayed even when nothing has been corrected. ([@jekuta][])
+* [#6380](https://github.com/rubocop-hq/rubocop/pull/6380): Allow use of a hyphen-separated frozen string literal in Emacs style magic comment. ([@y-yagi][])
 
 ### Changes
 
@@ -3620,3 +3621,4 @@
 [@lukasz-wojcik]: https://github.com/lukasz-wojcik
 [@albaer]: https://github.com/albaer
 [@Kevinrob]: https://github.com/Kevinrob
+[@y-yagi]: https://github.com/y-yagi

lib/rubocop/magic_comment.rb

@@ -140,7 +140,7 @@ def encoding
       private
 
       def extract_frozen_string_literal
-        match('frozen_string_literal')
+        match('frozen[_-]string[_-]literal')
       end
     end
 

spec/rubocop/magic_comment_spec.rb

@@ -73,6 +73,10 @@
                    '# fRoZeN-sTrInG_lItErAl: true',
                    frozen_string_literal: true
 
+  include_examples 'magic comment',
+                   '# -*- frozen-string-literal: true -*-',
+                   frozen_string_literal: true
+
   include_examples 'magic comment',
                    '# frozen_string_literal: invalid',
                    frozen_string_literal: 'invalid'