DUB saying my Linux exe file is "not an executable file" even though DUB built it

[WhatMeWorry via Digitalmars-d-learn]

$ sudo chmod -v 777 *
mode of 'HelloWindow' changed from 0644 (rw-r--r--) to 0777 
(rwxrwxrwx)
$ ls -al
total 3016
drwxr-xr-x 2 generic generic    4096 Aug 13 16:48 .
drwxr-xr-x 7 generic generic    4096 Aug 12 23:14 ..
-rw-r--r-- 1 generic generic 3080080 Aug 13 16:48 HelloWindow


Now I'm really gobsmacked.