$ cat x.scm
(declare (unit x))
(define (do-x) (print "do-x in x called."))

$ cat y.scm
(declare (unit y))
(define (do-y) (print "do-y in y called."))

$ cat z.scm
(declare (uses x y))
(do-x)
(do-y)

$ csc -c y.scm 
$ csc -c x.scm 
$ csc -static z.scm x.o y.o -o z
$ ./z
do-x in x called.
do-y in y called.
$