Fix snprintf compiler warning

sway/commands/output/background.c

@@ -112,7 +112,7 @@ struct cmd_results *output_cmd_background(int argc, char **argv) {
 						"Unable to allocate resources");
 			}
 
-			sprintf(src, "%s/%s", conf_path, rel_path);
+			snprintf(src, strlen(conf_path) + strlen(src) + 2, "%s/%s", conf_path, rel_path);
 			free(rel_path);
 			free(conf);
 		}

sway/server.c

@@ -214,7 +214,7 @@ bool server_init(struct sway_server *server) {
 	// Avoid using "wayland-0" as display socket
 	char name_candidate[16];
 	for (int i = 1; i <= 32; ++i) {
-		sprintf(name_candidate, "wayland-%d", i);
+		snprintf(name_candidate, sizeof(name_candidate), "wayland-%d", i);
 		if (wl_display_add_socket(server->wl_display, name_candidate) >= 0) {
 			server->socket = strdup(name_candidate);
 			break;