make the extracting lines for JRUBY optional throw using the DEBUG env variable

Fixes #3251

rakelib/vendor.rake

@@ -42,7 +42,7 @@ namespace "vendor" do
             next if stat.size == entry_size && (stat.mode & 0777) == entry_mode
           end
         end
-        puts "Extracting #{entry.full_name} from #{tarball} #{entry_mode.to_s(8)}"
+        puts "Extracting #{entry.full_name} from #{tarball} #{entry_mode.to_s(8)}" if ENV['DEBUG']
         File.open(path, "wb") do |fd|
           # eof? check lets us skip empty files. Necessary because the API provided by
           # Archive::Tar::Minitar::Reader::EntryStream only mostly acts like an