[PARCH 1/2, x86, PR63534] Fix darwin bootstrap

[Eric Botcazou]

> So that code creates a set of conflicts which, if I'm reading correctly,
> will prevent the PIC value from living in a register at all.  Which
> ought to result in it being dumped into the stack and being reloaded for
> each use.  Which ought to be safe (modulo the liveness bug Vlad is
> working on right now).
> 
> Does that sound right to either of you?

Yes, that's also my understanding of the code and the behavior required by 
builtin setjmp/longjmp.  I can add that the Ada compiler would fall apart if 
this didn't work correctly in the compiler, and especially in the RA.

-- 
Eric Botcazou