menhir.20260203 removed the deprecated MenhirLib.General. As a result, the current version of compcert on opam (3.16) no longer compiles with the current version on menhir.
I noticed that the corresponding file in this repository (cparser/ErrorReports.ml) has been updated 4 months ago to account for this deprecation. However, this change is currently not published on opam. So this issue will probably be resolved when a new version of compcert is released.