allow nfpvalues.py to be used for individual object files

import sys

def main(size_executable, rom_sections, ram_sections):

def main(size_executable, rom_sections, ram_sections, file="build/system.elf"):

    rom_sections = rom_sections.split(",")

    ram_sections = ram_sections.split(",")

    status = subprocess.run(

        size_executable.split() + ["-A", "build/system.elf"],

        size_executable.split() + ["-A", file],

        stdout=subprocess.PIPE,

        stderr=subprocess.PIPE,

        universal_newlines=True,