Don't eagerly create vendor/bundle/...
Don't eagerly create vendor/bundle/...

To avoid triggering warnings later that accuse developers of having
vendor/bundle in their repository.

[#148696219]

Signed-off-by: Forest Eckhardt <80a01a39b47e90d75c15574c906d1a0f1709496a@gmail.com>

cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack