How to use gexps in builds?

[nly]

...
(build-system trivial-build-system)
`(#:modules ((guix gexp))
         #:builder
         (gexp->derivation "gnumake"
                           #~(begin
                               (mkdir #$output)
                               (chdir #$output)
                               (symlink #$gnu-make #$output)))
         ))
...

The above form looks like it asks for too many (use-modules ...) (6 or
even more). What am I missing?