groups/2*.native_packages_*.group: adds dependencies.
    groups/231.native_packages_etc.group:apr:${PKG_NO_CLEAN}: don't clean due to reverse dependency on apr_util.
    groups/231.native_packages_etc.group:apr_util:${PKG_ENV_VARS_EXTRA}: build w/ LDADD_dbd_sqlite3=-lsqlite3 -lapr-1 -L.libs -laprutil-1.
    patches/apr_util-1.6.1.local.patch: removes obsolete patch.
    subr/pkg_clean.subr, vars/env.vars: don't clean if ${PKG_NO_CLEAN} is set.