DESTDIR[1] can be now set to specify the root in situations such as when
building a package or installing to a chrooted environment.

If not specified by environment variable (eg. by make) or in mkit.ini,
the default value is governed by MKIT_DEFAULT_DESTDIR, which defaults to
"/".

  [1]: https://www.gnu.org/prep/standards/html_node/DESTDIR.html