emacs: copy only needed stuff to qemu-treedir, not whole sysroot

* my typical sysroot is huge (5.5G) and only 86M is really needed
  we can also copy copy whole
  ${STAGING_DIR_TARGET}/${libdir}/lib*.so.*
  ${STAGING_DIR_TARGET}/${base_libdir}/l*
  but that is still quite big (3.2G)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>