Revert "[Fix build] Not rubygems, trying git config"

This reverts commit 4cdda6832ffb8841e02aba954a57428bb78898b8.
Revert "[Fix build] Use old rubygems (since that might be the problem)"

This reverts commit d8e5dcf9f9acbcf76ef92c22aa00808fea2e6745.