gperf-3.1 generates lookup functions that take a size_t length parameter instead of unsigned int. Test for this at configure time. Fixes: https://github.com/systemd/systemd/issues/5039
gperf-3.1 generates lookup functions that take a size_t length parameter instead of unsigned int. Test for this at configure time. Fixes: https://github.com/systemd/systemd/issues/5039