Hmm, well this explains the error. There should be a sourcefiles.txt file in the same folder as the win_makefile. I think there is a bug when you use clean=True on Windows. From the makefile, it seems that clean deletes sourcefiles.txt which I think it shouldn’t. Could you try running it without clean=True?
Building the code with clean=True is meant to call something make clean && make instead of a simple make. But if make clean removes a file that is necessary for the following make, this is not going to work…