py/nlrx64: Fixes to support Mac OS.
py/nlrx64: Fixes to support Mac OS.

Two independent fixes:
- need to prefix symbols referenced from asm with underscore;
- need to undo the C-function prelude.

blazewicz/micropython,alex-robbins/micropython,oopy/micropython,dmazzella/micropython,pfalcon/micropython,adafruit/micropython,adafruit/micropython,lowRISC/micropython,deshipu/micropython,infinnovation/micropython,kerneltask/micropython,toolmacher/micropython,SHA2017-badge/micropython-esp32,torwag/micropython,chrisdearman/micropython,adafruit/circuitpython,puuu/micropython,Peetz0r/micropython-esp32,bvernoux/micropython,blazewicz/micropython,Timmenem/micropython,TDAbboud/micropython,trezor/micropython,lowRISC/micropython,trezor/micropython,puuu/micropython,deshipu/micropython,adafruit/circuitpython,micropython/micropython-esp32,hiway/micropython,tralamazza/micropython,SHA2017-badge/micropython-esp32,pfalcon/micropython,cwyark/micropython,henriknelson/micropython,hiway/micropython,kerneltask/micropython,torwag/micropython,oopy/micropython,HenrikSolver/micropython,MrSurly/micropython,swegener/micropython,chrisdearman/micropython,adafruit/circuitpython,SHA2017-badge/micropython-esp32,AriZuu/micropython,chrisdearman/micropython,tobbad/micropython,lowRISC/micropython,dmazzella/micropython,tobbad/micropython,infinnovation/micropython,henriknelson/micropython,pfalcon/micropython,micropython/micropython-esp32,pozetroninc/micropython,oopy/micropython,selste/micropython,AriZuu/micropython,PappaPeppar/micropython,MrSurly/micropython,trezor/micropython,chrisdearman/micropython,toolmacher/micropython,selste/micropython,MrSurly/micropython-esp32,alex-robbins/micropython,tobbad/micropython,Peetz0r/micropython-esp32,micropython/micropython-esp32,hiway/micropython,pfalcon/micropython,PappaPeppar/micropython,tralamazza/micropython,ryannathans/micropython,puuu/micropython,oopy/micropython,ryannathans/micropython,Peetz0r/micropython-esp32,trezor/micropython,selste/micropython,PappaPeppar/micropython,HenrikSolver/micropython,tralamazza/micropython,kerneltask/micropython,toolmacher/micropython,henriknelson/micropython,HenrikSolver/micropython,infinnovation/micropython,MrSurly/micropython,AriZuu/micropython,chrisdearman/micropython,selste/micropython,adafruit/micropython,alex-robbins/micropython,pozetroninc/micropython,MrSurly/micropython,bvernoux/micropython,pramasoul/micropython,lowRISC/micropython,TDAbboud/micropython,Peetz0r/micropython-esp32,tobbad/micropython,kerneltask/micropython,ryannathans/micropython,PappaPeppar/micropython,bvernoux/micropython,tobbad/micropython,SHA2017-badge/micropython-esp32,alex-robbins/micropython,pozetroninc/micropython,Timmenem/micropython,Timmenem/micropython,Timmenem/micropython,TDAbboud/micropython,pozetroninc/micropython,swegener/micropython,kerneltask/micropython,cwyark/micropython,trezor/micropython,blazewicz/micropython,adafruit/circuitpython,henriknelson/micropython,micropython/micropython-esp32,MrSurly/micropython-esp32,torwag/micropython,pramasoul/micropython,pfalcon/micropython,selste/micropython,HenrikSolver/micropython,bvernoux/micropython,puuu/micropython,AriZuu/micropython,ryannathans/micropython,MrSurly/micropython-esp32,swegener/micropython,MrSurly/micropython-esp32,cwyark/micropython,infinnovation/micropython,MrSurly/micropython,torwag/micropython,dmazzella/micropython,Timmenem/micropython,tralamazza/micropython,deshipu/micropython,torwag/micropython,pramasoul/micropython,HenrikSolver/micropython,toolmacher/micropython,oopy/micropython,adafruit/micropython,Peetz0r/micropython-esp32,MrSurly/micropython-esp32,deshipu/micropython,deshipu/micropython,adafruit/micropython,toolmacher/micropython,PappaPeppar/micropython,SHA2017-badge/micropython-esp32,cwyark/micropython,dmazzella/micropython,lowRISC/micropython,alex-robbins/micropython,pramasoul/micropython,adafruit/circuitpython,swegener/micropython,hiway/micropython,TDAbboud/micropython,puuu/micropython,AriZuu/micropython,pramasoul/micropython,swegener/micropython,pozetroninc/micropython,micropython/micropython-esp32,cwyark/micropython,blazewicz/micropython,TDAbboud/micropython,hiway/micropython,infinnovation/micropython,bvernoux/micropython,henriknelson/micropython,ryannathans/micropython,blazewicz/micropython,adafruit/circuitpython