tree-wide: port all calls to alloca() to alloca_safe()

src/shared/firewall-util-iptables.c

@@ -128,7 +128,7 @@ int fw_iptables_add_masquerade(
         mr->rangesize = 1;
 
         /* Create a search mask entry */
-        mask = alloca(sz);
+        mask = alloca_safe(sz);
         memset(mask, 0xFF, sz);
 
         if (add) {

src/shared/nscd-flush.c

@@ -35,7 +35,7 @@ static int nscd_flush_cache_one(const char *database, usec_t end) {
         l = strlen(database);
         req_size = offsetof(struct nscdInvalidateRequest, dbname) + l + 1;
 
-        req = alloca(req_size);
+        req = alloca_safe(req_size);
         *req = (struct nscdInvalidateRequest) {
                 .version = 2,
                 .type = 10,