Earlier this week I found out that tumbleweed has dwarf unwinder disabled. This
happened when 4.9 was merged, as 4.9 stack dumping was completely rewritten by
Josh. The old unwinder is thus completely incompatible with the current code.

As a part of my work on dwarf unwinding (esp. assembly CFI annotations support
in objtool), I am fixing things up. I almost finished the port of our unwinder
to 4.9+.

I am only creating this as a tracker and as a heads-up that something is going
on.