Ensure "wrap" variable is non-NULL

RUNTIME_CHECK on the "wrap" variable avoids possible NULL dereference:

    thread.c: In function 'thread_wrap':
    thread.c:60:15: error: dereference of possibly-NULL 'wrap' [CWE-690] [-Werror=analyzer-possible-null-dereference]
       60 |         *wrap = (struct thread_wrap){

The RUNTIME_CHECK was there before
7d1ceaf.

Author: Mno-hime

lib/isc/thread.c

@@ -57,6 +57,7 @@ struct thread_wrap {
 static struct thread_wrap *
 thread_wrap(isc_threadfunc_t func, void *arg) {
 	struct thread_wrap *wrap = malloc(sizeof(*wrap));
+	RUNTIME_CHECK(wrap != NULL);
 	*wrap = (struct thread_wrap){
 		.func = func,
 		.arg = arg,