lib/net: avoid warning in log_if_name()

Newer GCC was issuing the following warning for the call of
strncpy() in log_if_name():

/usr/include/x86_64-linux-gnu/bits/string_fortified.h:95:10: warning: ‘__builtin_strncpy’ specified bound 32 equals destination size [-Wstringop-truncation]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |                                   __glibc_objsize (__dest));
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The warning is not proper because the code is already handling
string trucations.

This commit disable -Wstringop-truncation for that single call of
strncpy() using #pragma.

lib/net.c

@@ -1691,7 +1691,10 @@ log_if_name(char *if_name, size_t len, const struct gatekeeper_if *iface,
 		}
 	}
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstringop-truncation"
 	strncpy(if_name, iface->name, len);
+#pragma GCC diagnostic pop
 	if (unlikely(if_name[len - 1] != '\0')) {
 		G_LOG(CRIT, "%s(%s/%u): bug: len = %lu < strlen(iface->name) = %lu\n",
 			__func__, iface->name, port_id,