Sorry, I don’t know. I have no expirience with advanced scripting.
I even didn’t noticed the extra script in your project.
In my opinion, the copy thing via an extra script is way to complex.
Why don’t you configure the libraries via the platformio.ini as described here for the TFT_eSPI library? Then no extra script would be needed (which reduces the level of complexity and sources for possible errors).
– As written before – “just my opinion” 
I’m a fan of “keep it as simple as possible”