These are S-expressions, not Lisp. It's part of dune, which is the build system for ~40% of OPAM packages.
Dune is an unholy combination of bash and Lisp, according to its author - https://adam-mcdaniel.github.io/dune-website/
alt Hacker News
Dune is an unholy combination of bash and Lisp, according to its author - https://adam-mcdaniel.github.io/dune-website/