openbsd requires specifying the path for the [`find`][0] command. So this:

    find -name \*.o
    find: unknown option -- n
    usage: find [-dHhLXx] [-f path] path ... [expression]


fails.

This works:


    find . -name \*.o
    ./dist/build/Utility/Applicative.o
    ./dist/build/Utility/PosixFiles.o
    ./dist/build/Utility/Split.o
    ...


as expected.

Here's a patch for it: [0001-Makefile-Update-clean.patch][1].

[0]: https://man.openbsd.org/find
[1]: https://ricketyspace.net/patch/0001-Makefile-Update-clean.patch
