This drops function getexecname() redirection.
Historically `getexecname()` is a compatibility definition. Since openzfs has its own implementation of function `getexecname()` in `libspl` and has been merged into base, it is no longer needed.
Also without this fix `libspl` will end up an incompatible version of `getprogname()` with `libc`. In particular, if zfs is enabled, programs such as `pgrep` in `/rescue` can be wrongly statically linked with `libspl` and will not function properly.
PR: [[https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=269738 |269738]]
MFC after: 1 week
Fixes: 9e5787d2284e Merge OpenZFS support in to HEAD