d8e2056a8f
Historically, PKGDESTDIR was only set during pkg_install, and
XBPS_PKGDESTDIR was set to indicate that we're in subpkg's
pkg_install.
However, from 0b95cb8f5d, (Merge xbps-src code to make it usable in
a standalone mode., 2014-03-22), PKGDESTDIR is always set,
regardless of states.
Let's drop all usages of XBPS_PKGDESTDIR.
While we're at it, error out of vmove is used outside of subpkg.