nss-myhostname: fix maybe-uninitialized warning

nss-myhostname: fix maybe-uninitialized warning

In resolute with gcc 15.2.0:

472s ../src/nss-myhostname/nss-myhostname.c: In function ‘_nss_myhostname_gethostbyname4_r’:
472s ../src/nss-myhostname/nss-myhostname.c:132:44: error: ‘local_address_ipv4’ may be used uninitialized [-Werror=maybe-uninitialized]
472s   132 |                 *(uint32_t*) r_tuple->addr = local_address_ipv4;
472s       |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
472s ../src/nss-myhostname/nss-myhostname.c:42:18: note: ‘local_address_ipv4’ was declared here
472s    42 |         uint32_t local_address_ipv4;
472s       |                  ^~~~~~~~~~~~~~~~~~