"MicroPython continues to rock on with 1.8.1 release "
\m/ :D \m/
I have been interested in MicroPython for while due to a project I am working on. That requires a great level of portability of my python code. I have not been able, however, to compile a working standalone executable.
Try to follow README at https://github.com/micropython/micropython - it gives detailed (and simple) steps to build MicroPython. We also have continuous integration system ("build passing" badge in the same README), you can compare known good build process with what you get and see where it goes wrong for you. Finally, you can ask for help on the forum.