If you’ve never done this before, there is a fair amount to learn. It isn’t hard.
I made a few small edits to the makefile and STAR_smaller.C to target an ATTiny85. Next, I ran make. I pasted some of the output back here to show that it worked.
I can walk you through the edits if that would help.
What I flashed to the ’85 may not work. I don’t care since I was testing compile and flash.