> >    And run configure with --enable-shared (recommended).
> 
> I tried this one.
> But there is another problem:
> 
> There seems to be no Makefile in the ext/tcltlib directory of the ruby
> source tree.
> The compiler does not even touch any file in this directory.
> This can't be normal, can it?

I have no cygwin experience, but this sounds familiar anyway.
extconf.rb is supposed to generate the Makefile.

If it doesn't, it failed to detect tk properly.
I received some options to improve on detection earlier:

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/~poffice/mail/ruby-talk/17090

Good luck!

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