`missing .note.GNU-stack section` warnings with recent GNU ld

[fuhsnn]

Recent versions of ld would complain:

ld: warning: ... missing .note.GNU-stack section implies executable stack

on object files pcc generated.

A simple solution is to append ".section\t.note.GNU-stack,\"\",@progbits" to assembly outputs targeting gas + ld.

[ragge0]

Hm, I assume that this should only be present on targets that can turn off executable stack.
Also need to know when this should be emitted.