DNS resolv problem with glibc

Fix problem with dns resolv, by copying the libnss_dns.so to the rootfs.

Using glibc from external toolchain, name resolving does not work,
unless libnss_dns.so is available on the target.

Signed-off-by: Anders Darander <ad@datarespons.se>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>