unpack_strategy: fix unpack Dir.mktmpdir group

Otherwise the files will be unpacked with group wheel on macOS which
gets copied over when running `cp -al`.

Library/Homebrew/unpack_strategy.rb

@@ -160,6 +160,27 @@ module UnpackStrategy
     Dir.mktmpdir("homebrew-unpack", HOMEBREW_TEMP) do |tmp_unpack_dir|
       tmp_unpack_dir = Pathname(tmp_unpack_dir)
 
+      # Make sure files inside the temporary directory have the same group as the brew instance.
+      #
+      # @see https://github.com/Homebrew/brew/blob/4.4.0/Library/Homebrew/mktemp.rb#L57-L72
+      group_id = if HOMEBREW_BREW_FILE.grpowned?
+        HOMEBREW_BREW_FILE.stat.gid
+      else
+        Process.gid
+      end
+      begin
+        tmp_unpack_dir.chown(nil, group_id)
+      rescue Errno::EPERM
+        require "etc"
+        group_name = begin
+          Etc.getgrgid(group_id)&.name
+        rescue ArgumentError
+          # Cover for misconfigured NSS setups
+          nil
+        end
+        opoo "Failed setting group \"#{group_name || group_id}\" on #{tmp_unpack_dir}"
+      end
+
       extract(to: tmp_unpack_dir, basename:, verbose:)
 
       children = tmp_unpack_dir.children