From: "fkc_email-news @ yahoo dot com" <fkchang2000 / gmail.com>
Subject: compiling ruby/tk on 64 bit Redhat?
Date: Thu, 16 Nov 2006 03:20:14 +0900
Message-ID: <1163614575.276369.186180 / f16g2000cwb.googlegroups.com>
>   From reading the mkmf.log, I"m guessing it's not picking
> /usr/X11R6/lib64 as the lib directory when it's trying to discover
> libs.  It does try /usr/X11R6/lib, however.  I can't seem to figure out
> a way to get it to add that search dir.  Guesses at adding with-x-lib
> or with-x11-lib didn't seem to do it.

Please try "--with-X11-lib=/usr/X11R6/lib64".
                   ^(uppercase)

I think that "--with-X11-dir". "--with-X11-include", and 
"--with-X11-lib" must be available. 
After trying, please report the result to this ML.
-- 
Hidetoshi NAGAI (nagai / ai.kyutech.ac.jp)