RUBYGEMS install on AIX zlib not found

I read all the posts on zlib but cannot find an answer … .
I installed ruby on AIX 4.3.3 from tar.gz. My ext/zlib contains zlib.o
and zlib.so. make test produces no errors. However, when I run ruby
setup.rb from rubygems install, I get “no such file …”

Please help me install zlib in the proper place.

/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:in
require__': no such file to load -- zlib (LoadError) from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems/package.rb:9
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:in
require' from /usr/local/lib/ruby/site_ruby/1.8/rubygems/builder.rb:1 from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:inrequire’
from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:61:in
manage_gems' from /tmp/rubygems-0.8.11/./post-install.rb:64:ininstall_sources’
from /tmp/rubygems-0.8.11/./post-install.rb:75:in try_run_hook' from setup.rb:577:inrun_hook’
from setup.rb:1315:in exec_task_traverse' from setup.rb:1168:inexec_install’
from setup.rb:887:in exec_install' from setup.rb:705:ininvoke’
from setup.rb:674:in `invoke’
from setup.rb:1352