Due to a typo in the spec, the issue was not caught initially. If
Bundler does not need to re-resolve, `bundle lock` is a noop so Bundler
does not add checksums.

To fix the issue, we do something similar to what `bundle install` does,
just without actually installation. First set the domain (local or
remote) according to whether a re-resolve is necessary, and then
materialize lazy specifications into real specifications, so that
checksums are actually fetched from each source.

https://github.com/rubygems/rubygems/commit/84b6f4ee96