Make sure to define _GNU_SOURCE before including netdb.h
This fixes the Musl build as it only defines NI_MAXHOST when _GNU_SOURCE is set. https://git.musl-libc.org/cgit/musl/tree/include/netdb.h#n147
This fixes the Musl build as it only defines NI_MAXHOST when _GNU_SOURCE is set. https://git.musl-libc.org/cgit/musl/tree/include/netdb.h#n147