Relative directory paths w/i platform io in Python script

I am attempting to use some specific relative paths within a platform I have created, and I cannot seem to figure out how to use them within the Python builder scripts. I know that the absolute paths to packages can be found with the ‘get_package_dir’ function, but is there any way to get something like the platformIO core path or similar? I mainly want to include a couple of small files in the platform without the overhead of creating a new package.

I had been trying to use an environment variable to retrieve this, but that doesn’t seem to be working, most likely because it was never explicitly set. Would this be possible by modifying PATH?