You can exclude the option definition just by postfixing a conditional, e.g. `option 'enable-multilib', 'Build with multilib support'  if MacOS.prefer_64_bit?` `build.include?` will still register for it so you'll need to check for it in the install method. You could just start the if statement:

```ruby
if build.include? 'enable-multilib'  && MacOS.prefer_64_bit?
```

(Though I need to check if multilib is also broken on powerpc64)