add dlerror message for static-linked dlsym failure

src/ldso/dynlink.c

@@ -1609,6 +1609,8 @@ void *dlopen(const char *file, int mode)
 }
 void *__dlsym(void *restrict p, const char *restrict s, void *restrict ra)
 {
+	errflag = 1;
+	snprintf(errbuf, sizeof errbuf, "Symbol not found: %s", s);
 	return 0;
 }
 int __dladdr (const void *addr, Dl_info *info)