When building a 64bit version of rubyx for x86_64, I configure with
 ... --libdir=/pkg/ruby.1/lib64 ...

Installation works as expected except that the search paths do not reflect my 
choice of libdir; Ie lib should be lib64 when I do this...

root@orac / # ruby -e 'puts $:.join("\n")'
/lib/ruby/site_ruby
/pkg/ruby.1/lib/ruby/site_ruby/1.8
/pkg/ruby.1/lib/ruby/site_ruby/1.8/x86_64-linux
/pkg/ruby.1/lib/ruby/site_ruby
/pkg/ruby.1/lib/ruby/1.8
/pkg/ruby.1/lib/ruby/1.8/x86_64-linux
.

No I can get around this with symlinks or RUBYLIB, but I guess it should be 
fixed.

Hope thats useful

Andrew Walrond