make-symbolic-link
make-symbolic-link is an interactive built-in function in `C source code
'.
(make-symbolic-link FILENAME LINKNAME &optional OK-IF-ALREADY-EXISTS)
Make a symbolic link to FILENAME, named LINKNAME.
Both args must be strings.
Signals a `file-already-exists' error if a file LINKNAME already exists
unless optional third argument OK-IF-ALREADY-EXISTS is non-nil.
A number as third arg means request confirmation if LINKNAME already exists.
This happens for interactive use with M-x.