have opt alias symlink point into the Cellar

in case people expect to be able to find the prefix by only resolving
the symlink once (e.g., if they're using readlink not realpath)

Library/Homebrew/keg.rb

@@ -479,7 +479,7 @@ class Keg
     aliases.each do |a|
       alias_opt_record = opt_record.parent/a
       alias_opt_record.delete if alias_opt_record.symlink? || alias_opt_record.exist?
-      make_relative_symlink(alias_opt_record, opt_record, mode)
+      make_relative_symlink(alias_opt_record, path, mode)
     end
 
     return unless oldname_opt_record