Auto merge of #5675 - bundler:seg-specs-resilient-against-rubylib-shims, r=segiddins
Auto merge of #5675 - bundler:seg-specs-resilient-against-rubylib-shims, r=segiddins

Make the setup specs resilient agains ruby shims setting RUBYLIB

Rbenv in particular does this

mvz/bundler,bundler/bundler,bundler/bundler,dilumnavanjana/bundler,mvz/bundler,dilumnavanjana/bundler