runtime/internal/lib/os: fix readdir for darwin-amd64

_demo/readdir/main.go

@@ -13,7 +13,17 @@ func main() {
 	if len(entries) == 0 {
 		panic("No files found")
 	}
+	var check int
 	for _, e := range entries {
 		fmt.Printf("%s isDir[%t]\n", e.Name(), e.IsDir())
+		if !e.IsDir() {
+			switch e.Name() {
+			case "go.sum", "go.mod":
+				check++
+			}
+		}
+	}
+	if check != 2 {
+		panic("Bad readdir entries go.mod/go.sum")
 	}
 }