incorrect base_dir for default gemspecs
gemspecs for default gems have incorrect path since they're installed in a subdirectory of the normal specifications path. The base_dir is dirname(dirname(loaded_from)), so using an additional subdir results in a base_dir that's "off by one." Example:
Find the gemspec for the default rake gem:
spec = Gem::Specification.find_by_name('rake')
=> #<Gem::Specification:0x3fc3fa4dd570 rake-0.9.5>
The spec.base_dir should be "/Users/jeremy/.rbenv/versions/2.0.0-preview2/lib/ruby/gems/2.0.0"
This means Gem.bin_path lookups in bin/rake, etc result in incorrect executable paths: