Default build on linux x86_64 needs libruby.so.1.9 at runtime

[ericpromislow]

Bring up irb 1.9.3 and move to a directory containing trace_nums19.so

irb(main):002:0> require './trace_nums19.so'
LoadError: libruby.so.1.9: cannot open shared object file: No such file or directory - /.../trace_nums19.so
from /.../custom_require.rb:36:in require' from /.../custom_require.rb:36:inrequire'
from (irb):2
from /.../ruby-1.9.3-p125/bin/irb:12:in `

'

Can someone clue me in on why this message? I'm running Ruby 1.9 -- why does it need to load the shared library?