Use more tough server: GitHub or repo.or.cz

https://gcc.gnu.org/wiki/GitMirror

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52761 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/downloader.rb

@@ -40,7 +40,11 @@ class Downloader
 
   class GNU < self
     def self.download(name, *rest)
-      super("#{https}://gcc.gnu.org/git/?p=gcc.git;a=blob_plain;f=#{name};hb=master", name, *rest)
+      if https == 'https'
+        super("https://raw.githubusercontent.com/gcc-mirror/gcc/master/#{name}", name, *rest)
+      else
+        super("http://repo.or.cz/official-gcc.git/blob_plain/HEAD:/#{name}", name, *rest)
+      end
     end
   end