powerpc: Set better default compiler.
powerpc: Set better default compiler.

Most developers use a compiler which is called powerpc64le-linux-gnu-gcc.

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