Use sudo for symlinks if necessary.

Library/Homebrew/cask/artifact/symlinked.rb

@@ -43,7 +43,7 @@ def summarize_installed
 
       private
 
-      def link(force: false, **options)
+      def link(force: false, command: nil, **options)
         unless source.exist?
           raise CaskError,
                 "It seems the #{self.class.link_type_english_name.downcase} " \
@@ -64,19 +64,20 @@ def link(force: false, **options)
         end
 
         ohai "Linking #{self.class.english_name} '#{source.basename}' to '#{target}'"
-        create_filesystem_link(**options)
+        create_filesystem_link(command: command)
       end
 
       def unlink(**)
         return unless target.symlink?
 
         ohai "Unlinking #{self.class.english_name} '#{target}'"
-        target.delete
+        Utils.gain_permissions_remove(target, command: command)
       end
 
-      def create_filesystem_link(command: nil, **_)
+      def create_filesystem_link(command: nil)
         target.dirname.mkpath
-        command.run!("/bin/ln", args: ["-h", "-f", "-s", "--", source, target])
+        command.run! "/bin/ln", args: ["-h", "-f", "-s", "--", source, target],
+                                sudo: !target.dirname.writable?
         add_altname_metadata(source, target.basename, command: command)
       end
     end