I tried hacking jekyll to work with files/dirs the way I wanted but failed. So, I wrote this ridiculous build script in PHP.
build.php
expects an output dir and a hostname.
php build.php public http://localhost:8000
To test the output locally (it's just HTML files) just run:
php -S localhost:8000 -t public/
index.php
expects the output dir to be public/
.