[ruby-cvs:78300] 8eb0a9e566 (master): Use jsDelivr instead of raw.githubusercontent.com

Kazuhiro NISHIYAMA	2019-11-22 13:55:59 +0900 (Fri, 22 Nov 2019)

  New Revision: 8eb0a9e566

  https://github.com/ruby/ruby/commit/8eb0a9e566

  Log:
    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
    ```

  Modified files:
    tool/downloader.rb