Composer binary built when installed

Composer package can include vendor binary. If my repository has a file "bin/foobar.phar" in it, I can add this to my composer.json:

{
    "name": "foobar/cli",
    "bin": ["bin/foobar.phar"]
}

Then when I install this "foobar/cli" package, the file "bin/foobar.phar" will be installed to "vendor/bin".

My question is how do I do this without commiting the "bin/foobar.phar" file to my repository? Let say I can build the file by running the script "composer build":

{
    "name": "foobar/cli",
    "scripts": {
        "build": "@php build.php --target=./bin/foobar.phar"
    },
    "bin": ["bin/foobar.phar"]
}

How do I setup my repository so the bin target is built when installed by project depends on "foobar/cli"?

I've tried to put "@composer build" into the following event hooks, none seems to work:

• pre-install-cmd
• post-install-cmd
• pre-update-cmd
• post-update-cmd
• pre-package-install
• post-package-install
• pre-package-update
• post-package-update

Package like phpunit seems to have pulled this off. There should be a way for it.

Please suggest what I should try. Thanks.