feat(prod_image_util): Moving ld.so configs to /usr

Moving the ld.so configs to /usr and symlinking them to /. This allows
images with a tmpfiles root (e.g. PXE) to have ld.so config support.
Merge pull request #228 from crawford/ld.so

feat(prod_image_util): Adding support for ld.so configs on tmpfs roots