Fix brew unpack --patch

Applying patches in `brew unpack` was broken since b76e26c9cf1f
("Decouple applying patches from staging the source").

Closes Homebrew/homebrew#38997.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Homebrew/cmd/unpack.rb

@@ -2,12 +2,6 @@ require "stringio"
 require "formula"
 
 module Homebrew
-  module UnpackPatch
-    def patch
-      super if ARGV.flag?("--patch")
-    end
-  end
-
   def unpack
     formulae = ARGV.formulae
     raise FormulaUnspecifiedError if formulae.empty?
@@ -22,7 +16,6 @@ module Homebrew
     raise "Cannot write to #{unpack_dir}" unless unpack_dir.writable_real?
 
     formulae.each do |f|
-      f.extend(UnpackPatch)
       stage_dir = unpack_dir.join("#{f.name}-#{f.version}")
 
       if stage_dir.exist?
@@ -33,7 +26,10 @@ module Homebrew
       oh1 "Unpacking #{f.name} to: #{stage_dir}"
 
       ENV['VERBOSE'] = '1' # show messages about tar
-      f.brew { cp_r getwd, stage_dir }
+      f.brew do
+        f.patch if ARGV.flag?("--patch")
+        cp_r getwd, stage_dir
+      end
       ENV['VERBOSE'] = nil
 
       if ARGV.git?