Downloader: retry when RFC 2616 noncompliant dates [ci skip]

zlib.net rarely returns the current time in RFC 2616 noncompliant
format in the response header, and the checksum does not match in
that case (maybe creating the tarball on the fly?).

tool/downloader.rb

@@ -211,9 +211,15 @@ class Downloader
       $stdout.print "downloading #{name} ... "
       $stdout.flush
     end
+    mtime = nil
+    options = options.merge(http_options(file, since.nil? ? true : since))
     begin
       data = with_retry(10) do
-        url.read(options.merge(http_options(file, since.nil? ? true : since)))
+        data = url.read(options)
+        if mtime = data.meta["last-modified"]
+          mtime = Time.httpdate(mtime)
+        end
+        data
       end
     rescue OpenURI::HTTPError => http_error
       if http_error.message =~ /^304 / # 304 Not Modified
@@ -237,16 +243,13 @@ class Downloader
       end
       raise
     end
-    mtime = nil
     dest = (cache_save && cache && !cache.exist? ? cache : file)
     dest.parent.mkpath
     dest.open("wb", 0600) do |f|
       f.write(data)
       f.chmod(mode_for(data))
-      mtime = data.meta["last-modified"]
     end
     if mtime
-      mtime = httpdate(mtime)
       dest.utime(mtime, mtime)
     end
     if $VERBOSE
@@ -328,7 +331,7 @@ class Downloader
     times = 0
     begin
       block.call
-    rescue Errno::ETIMEDOUT, SocketError, OpenURI::HTTPError, Net::ReadTimeout, Net::OpenTimeout => e
+    rescue Errno::ETIMEDOUT, SocketError, OpenURI::HTTPError, Net::ReadTimeout, Net::OpenTimeout, ArgumentError => e
       raise if e.is_a?(OpenURI::HTTPError) && e.message !~ /^50[023] / # retry only 500, 502, 503 for http error
       times += 1
       if times <= max_times