The current release (not master) of micropython is using the commit id of the ESP32 beta 4 SDK. At the time this release was made esp32 support had compile issues. Those issues were quickly fixed in micropython master, however the release tag is in front of those fixes. lv_micropython is only ported to releases of micropython so those build issues got ported into lv_micropython.
https://forum.littlevgl.com/t/esp32-micropython-build-errors-lots/1754

These issues can be fixed with a few edits, but a new micropython release would cure the problem by moving onto the released ESP32 4 SDK.

Note: if you install the ESP compiler using the ESPIDF3 method you won't encounter this. If you install the compiler using the new install script in ESPIDF4 you'll hit it.