binutils execstack warnings still emitted after #762

[zhibukeduo]

linker still warns on nightly (binutils 2.46):

z80-none-elf-ld: warning: putchar.ce.o: missing .note.GNU-stack section implies executable stack
z80-none-elf-ld: warning: obj/crt0.o: missing .note.GNU-stack section implies executable stack