Reproducibility problems with rubygems

[Arthur Gautier]

Hello everyone,

When investigating reproducibility problems with rubygems over at
NixOS, we found this issue:
https://github.com/rubygems/rubygems/pull/4610
Not sure this is the place to post this (let me know if there is a
better place to), but I thought it might benefit other distributions
as well.

If I read git history correctly, all versions of rubygems since v2.5.2
have been affected.

Best,
--
Arthur