build-micropython.sh: new URL, build micropython.bin
build-micropython.sh: new URL, build micropython.bin

Updated git repo URL for micropython.git; re-enabled building of combined
micropython.bin as it is useful on Nuamto Mimas v2.  Tested with lm32
soft CPU; appears not to work with or1k soft CPU at this time ("system.h
not found")

mithro/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware