build warnings when HAVE_INET6 is off

[alfredh]

Debian 11:

alfredh@debian:~/git/re$ make HAVE_INET6= HAVE_INET6_IGNORE_DEPRECATED=1 1>/dev/null
src/http/client.c: In function ‘http_client_set_laddr6’:
src/http/client.c:1111:46: warning: unused parameter ‘cli’ [-Wunused-parameter]
 1111 | void http_client_set_laddr6(struct http_cli *cli, const struct sa *addr)
      |                             ~~~~~~~~~~~~~~~~~^~~
src/http/client.c:1111:68: warning: unused parameter ‘addr’ [-Wunused-parameter]
 1111 | void http_client_set_laddr6(struct http_cli *cli, const struct sa *addr)
      |                                                   ~~~~~~~~~~~~~~~~~^~~~
src/dns/client.c: In function ‘dnsc_alloc’:
src/dns/client.c:859:19: warning: unused variable ‘laddr6’ [-Wunused-variable]
  859 |  struct sa laddr, laddr6;
      |                   ^~~~~~
src/sa/sa.c: In function ‘sa_set_scopeid’:
src/sa/sa.c:696:45: warning: unused parameter ‘scopeid’ [-Wunused-parameter]
  696 | void sa_set_scopeid(struct sa *sa, uint32_t scopeid)
      |                                    ~~~~~~~~~^~~~~~~

it would be nice if building with this option gave zero warnings ...