nrf/Makefile: Refine dead-code elimination parameters.
nrf/Makefile: Refine dead-code elimination parameters.

Clang warns about useless -Wl,--gc-sections passed in CFLAGS.

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