Since we started locking the specific platform in the lockfile, that has
created an annoying situation for users that don't develop on Linux.
They will create a lockfile on their machines, locking their local
platform, for example, darwin. But then that lockfile won't work
automatically when deploying to Heroku for example, because the lockfile
is frozen and the Linux platform is not included.
There's the chance though that resolving against two platforms (Linux +
the local platform) won't succeed while resolving for just the current
platform will. So, instead, we check other platform specific variants
available for the resolution we initially found, and lock those
platforms and specs too if they satisfy the resolution.
This is only done when generating new lockfiles from scratch, existing
lockfiles should keep working as before, and it's only done for "ruby
platforms", i.e., not Java or Windows which have their own complexities,
and so are excluded.
With this change, we expect that MacOS users can bundle locally and
deploy to Heroku without needing to do anything special.
https://github.com/rubygems/rubygems/commit/5f24f06bc5