Ok, so I've made some (minor) progress.
I have learned that the setting I need to change is OIT. I need to change this to "HAVE_OIT=1" in the Makefile.
Problem is, I have no clue what the Makefile is or where it is located. Anybody know where I can find this file? Or if it even exists in Batocera? If it does not exist is there a way to generate this file?