Unix/Linux/FreeBSD and Macintosh only: A list value means that the saved image is a dynamic library file rather than an executable. The build machine must have a C compiler installed.
If non-nil, dll-added-files should be a list of filenames and then a dynamic library containing each named file is saved. Each file must be of a format that the default C compiler can incorporate into a shared library and must not contain exports that clash with predefined exports in the LispWorks shared library. The added files are useful to write wrappers around calls into the LispWorks dynamic library.
LispWorks User Guide and Reference Manual
for more details.
For more information about the behavior of LispWorks DLLs (dynamic libraries) see the chapter "LispWorks as a dynamic library" in the LispWorks User Guide and Reference Manual .
LispWorks Delivery User Guide - 13 Dec 2011