Original code is in https://github.com/altbdoor/jekyll-exe, and modified to run with GitHub actions.
Check the releases page for downloads.
OCRA only supports up to Ruby 2.1, and does not seem to be supported anymore.
As far as Jekyll is concerned, only v3.9.x still supports Ruby 2.1, and a lot of the dependencies have also moved on.
A lot of version pinning is done to make things work, but it also means the binaries are running on very outdated libraries.
I was unable to build v3.9.2, and I'm giving up. The better part of internet has moved on to v4.x anyways.
Cheers!