Request: ppx_optcomp to support reading environment variables at compile time

Hi,

Related discussion:

https://discuss.ocaml.org/t/ppx-getenv-dune-compatible-alternative/4082

It would be useful if I could control the compilation via an environment variable, similar to the ppx_getenv example by whitequark (which doesn't work with dune).

Are there plans to add this?

Thanks!

Start by reading the related OCaml discussion linked in the issue and reviewing the existing ppx_optcomp behavior. No files, tests, or entry points are named, so first determine where compile-time options are handled and how dune compatibility should work. Done means environment variables can reliably control compilation through ppx_optcomp.

Written by the indexing model from the issue text.