Use the variable *system-configuration-mappings* to find
an output path for the source. The algorithm transforms each
entry in possible-paths as follows: If there is a mapping
whose source starts with the path of possible-path, then
replace possible-path with a pathname that starts with the
target of the mapping and continues with the rest of
possible-path. If no such mapping is found, then use the
default mapping.

If *centralize-lisp-binaries* is false, then the default
mapping is to place the output in a subdirectory of the
source. The subdirectory is named using the Lisp
implementation (see
implementation-specific-directory-name). If
*centralize-lisp-binaries* is true, then the default
mapping is to place the output in subdirectories of
*default-toplevel-directory* where the subdirectory
structure will mirror that of the source.