sitedir is not included in $LOAD_PATH (Ruby 1.8.5 on NetBSD)
I didn't use pkgsrc.

============= RUBY 1.8.5 ================
irb(main):001:0> $LOAD_PATH
=> ["/1.8", "/1.8/i386-netbsdelf3.0.1", "", "/home/vee/lib/ruby/1.8",
"/home/vee/lib/ruby/1.8/i386-netbsdelf3.0.1", "."]

============= RUBY 1.8.4 ================
irb(main):001:0> $LOAD_PATH
=> ["/home/vee/lib/ruby/site_ruby/1.8",
"/home/vee/lib/ruby/site_ruby/1.8/i386-netbsdelf3.0.1",
"/home/vee/lib/ruby/site_ruby", "/home/vee/lib/ruby/1.8",
"/home/vee/lib/ruby/1.8/i386-netbsdelf3.0.1", "."]