title: buildroot: How to add *.so lib
body: <p>I am working on project to debug linux kernel. I use qemu with buildroot image.</p>
  <p>Some programs that are used for test use external libraries.
  For example pthread library is already included into buildroot and the programs with pthread functions run on qemu. But when the programs built with external libraries launched on qemu produce error function not implemented.</p>
  <p>Question is how to add *.so lib file into buildroot to generate rootfs with the external libraries included?</p>