Deployment issue with Laravel on Heroku

Question

I am trying to deploy a Laravel app to Heroku. I am getting an error relating to a custom compile script in composer.json:

Running 'composer compile'...
remote:        > @php -d phar.readonly=0 bin/compile > ~/log.txt
remote:        Script @php -d phar.readonly=0 bin/compile > ~/log.txt handling the compile event returned with error code 1
remote:
remote:  !     ERROR: Compile step failed!
remote:  !
remote:  !     Installation of dependencies was successful, but the custom
remote:  !     script you're using to perform actions after 'composer install'
remote:  !     failed with the error above.
remote:  !
remote:  !     Check that the 'compile' command(s) in the 'scripts' section of
remote:  !     your 'composer.json' are working properly and not running into
remote:  !     timeouts or memory limits.

The scripts section of composer.json looks like this:

"scripts": {
    "compile": "@php -d phar.readonly=0 bin/compile",
    "test": "simple-phpunit"
}

I have no idea what bin/compile is or if it even exists. I took over this project from someone who did not document any of their code so I am struggling to put the pieces together.