Update shim for ocamlrep (#2043)

Summary:
X-link: https://github.com/facebook/buck2/pull/574
Pull Request resolved: https://github.com/pytorch/executorch/pull/2043

I messed the ocamlrep changes to this file when I initially stood up the unified shims directory, adding this will help that project build correctly with buck2 on github.

bypass-github-export-checks

Reviewed By: jailby

Differential Revision: D54074479

fbshipit-source-id: 0a24c48243addad2f3118a09ff6cef96d478b0ab