Make python detection more robust and allow setting PYTHON2 and PYTHON3 to override python executables during build.
Make python detection more robust and allow setting PYTHON2 and PYTHON3 to override python executables during build.

adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython,adafruit/micropython,adafruit/micropython,adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython