Use jsDelivr instead of raw.githubusercontent.com
Try to fix download error on Solaris CI
https://rubyci.org/logs/rubyci.s3.amazonaws.com/unstable11x/ruby-master/log/20191121T162422Z.fail.html.gz
tool/downloader.rb:243:in `rescue in download': failed to download config.guess (RuntimeError) Net::HTTPFatalError: 503 "Service Unavailable": https://raw.githubusercontent.com/gcc-mirror/gcc/master/config.guess
Use jsDelivr instead of raw.githubusercontent.com
Try to fix download error on Solaris CI
https://rubyci.org/logs/rubyci.s3.amazonaws.com/unstable11x/ruby-master/log/20191121T162422Z.fail.html.gz