So I had the same requirement - I needed to modify that file for some changes to GCM. I did it the "low tech" way. I have a modified copy of that file in a project folder and inside hooks/before_prepare I created a script that copies the file into the right place
You can see my approach here https://github.com/pliablepixels/zmNinja/blob/master/hooks/before_prepare/01_pp_hacks.sh#L11
Note: You should ideally write this as a nodejs script so its completely portable, I wrote it as a shell script because I was more familiar with it.