This keyword takes a list of packages to be retained. All packages in the list are kept in the delivered image, regardless of the values of the :smash-packages and :delete-packages keywords.
:all, then the two variables above are set to
nil. See also Coping with intern and find-symbol at runtime.
Other keywords push packages onto the
When you keep a package by
:packages-to-keep, this does not cause that package's symbols to be kept. To retain symbols, see Ensuring that symbols are kept.
LispWorks Delivery User Guide - 15 Feb 2015