- overridable by having a log service at `$pkgname/files/$service/log`
- warns if stderr is not redirected in the main service
- uses a sane default run script with the service name set as tag and
daemon facility
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.
Those helpers were just setting up some extra functions that can be used
on templates, and this can be done already via environment, so let's remove
the helpers completely.