Build failure related to lseek64 on osx in build-repro ci

See for example https://gitlab.torproject.org/tpo/core/arti/-/jobs/501742 :

/arti/osxcross/build/apple-libtapi/src/llvm/lib/Support/raw_ostream.cpp:834:11: error: no member named 'lseek64' in the global namespace; did you mean 'lseek'?
  834 |   pos = ::lseek64(FD, off, SEEK_SET);
      |         ~~^~~~~~~
      |           lseek
/usr/include/unistd.h:46:7: note: 'lseek' declared here
   46 | off_t lseek(int, off_t, int);
      |       ^