composer: Forward STDIN to sub-processes (was: Composer post-install-cmd php script doesn't wait for input)

So I have a console script i want run after composer has run an install.

"scripts": {
    "post-install-cmd": [
        "sudo ./bin/phing -f ./phing/builds/nginx/build.xml"
    ]
}

When I run

$ sudo ./bin/phing -f ./phing/builds/nginx/build.xml 

manually form the command line - no problems. As expected. However when I run

$ composer install 

the file executes but STDIN does not wait for a response.