Reproducible repository for: rubygems/rubygems#4123

To reproduce you can execute:

docker run --rm -it -v $PWD:/src ruby:2.5 /src/platform-bug

# Update rubygems
docker run --rm -it -v $PWD:/src  -e RUBYGEMS_UPDATE=1 ruby:2.5/src/platform-bug

docker run --rm -it -v $PWD:/src ruby:2.6 /src/platform-bug

# Update rubygems
docker run --rm -it -v $PWD:/src  -e RUBYGEMS_UPDATE=1 ruby:2.6/src/platform-bug

docker run --rm -it -v $PWD:/src ruby:2.7 /src/platform-bug