[arm] Use EABI unwind library

[Mark Mitchell]

Richard Earnshaw wrote:

>>I'm pretty uncomfortable with putting this on the mainline.  I know that 
>>we need this for full EABI compatibility in 4.0 -- but I think this is 
>>not Stage 3 material, due to the changes to gcc/except.c and the V3 
>>bits, even though I see that those are pretty minimal.  Let's queue this 
>>for 4.1.  (Our internal Wiki has a list of ARM patches queued for 4.1 -- 
>>presently empty.)  If Richard E. wants to lobby for this in 4.0 after he 
>>comes back from vacation, he can try to convince Richard Henderson (EH) 
>>and Benjamin Koznik (V3); I'd feel differently if those folks wanted to 
>>go ahead with this patch as well, but I feel tremendously uncomfortable 
>>approving this directly.
>>    
>>
>
>The problem with this is that without this code the C++ compiler is so
>fundamentally non-compliant that we might as well disable building of
>G++ entirely.  And that means we'd have to wait nearly another year[1]
>before we had an FSF release that was compliant.
>  
>
I think that, then, you should try to convince Richard Henderson and 
Benjamin Koznik that these changes are valuable.  If it is OK with them, 
I would be OK with it, but I do not want to push changes into subsytems 
that I do not maintain in a way that could be perceived as a favor for a 
CodeSourcery customer.  I'd also be open to a conditional compilation 
solution; if Richard H. feels uncomfortable with the EH changes, maybe 
he'd be happier with them #ifdef'd.

I think the worst case is that we create csl-arm-4_0-branch, which 
differs from the 4_0-branch only by this patch.

-- 
Mark Mitchell
CodeSourcery, LLC
(916) 791-8304
mark@codesourcery.com