tools/makemanifest.py: Use sys.executable when invoking Python scripts.
tools/makemanifest.py: Use sys.executable when invoking Python scripts.

So the version of Python used to run makemanifest.py is also used for the
sub-scripts.

pozetroninc/micropython,selste/micropython,MrSurly/micropython,pramasoul/micropython,adafruit/circuitpython,bvernoux/micropython,selste/micropython,bvernoux/micropython,trezor/micropython,kerneltask/micropython,adafruit/circuitpython,pozetroninc/micropython,trezor/micropython,henriknelson/micropython,MrSurly/micropython,kerneltask/micropython,adafruit/circuitpython,selste/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,trezor/micropython,kerneltask/micropython,pramasoul/micropython,pozetroninc/micropython,kerneltask/micropython,adafruit/circuitpython,henriknelson/micropython,MrSurly/micropython,tobbad/micropython,pramasoul/micropython,pozetroninc/micropython,henriknelson/micropython,pramasoul/micropython,MrSurly/micropython,bvernoux/micropython,adafruit/circuitpython,tobbad/micropython,kerneltask/micropython,trezor/micropython,henriknelson/micropython,trezor/micropython,tobbad/micropython,selste/micropython,bvernoux/micropython,tobbad/micropython,MrSurly/micropython,tobbad/micropython,pramasoul/micropython,selste/micropython,pozetroninc/micropython