centos 6.3 -> 6.4.
configure dns in chroot tree.
add "tar" command to build ruby-binary in chroot.
update code layout.
merge createrepo-vdc.sh into spot-build.sh.
rpmbuild: remove unnecessary codes.
update code layout.
update code layout.
remove rootfs-tree tarball dependency.
use "setarch" command to set build-archtecture.
Revert "use "setarch" command to set build-archtecture."

This reverts commit b7279f3d655a76987d3ecd1f4fd11d6318c10b70.
Revert "remove rootfs-tree tarball dependency."

This reverts commit a72599743c4bb6f1dd7f2c829fb290f85286e7dc.
Merge branch 'refactor-rpmbuild'