Always create usr/local/etc -> /etc/local symlink

/usr/local/etc gets created and populated by packages. However, if no
packages are installed when setup_nanobsd is run, this symlink won't
get created, causing problems if packages are installed later (say on
first boot). Therefore, always create the symlink and etc/local. It
does no harm and may help.

Inspired by crochet issue #183 (consuingly says NanoBSD, means crochet)
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