This is fixable by simply adding --disable-rubygems to the configure command in build()

This doesn't solve #3406 though. Bundled gems such as ruby-rake appear to still be broken, as before. But at least the extra error is gone.

/usr/bin/rake:9:in `require': cannot load such file -- rubygems (LoadError)
        from /usr/bin/rake:9:in `<main>'

which package configure command? 'ruby'? or each client?

also, note that this ticket is about the "RubyGems were not
loaded" warning - the "rubygems (LoadError)" error is handled on
ticket #3406