[patch] Don't produce stubs on darwin x86

[Rafael Espíndola]

>> The attached patches disable the production of stubs on darwin x86.
>> These were needed with older linkers, but Jim mentioned that using
>> older tools (about 6 years in this case I think) with current clang is
>> not supported.
>>
>> The existing code also confuses the linker version with the OS being
>> targeted. My understanding is that with this patch it is still
>> possible to build code that will run on OS X 10.4, one just needs a
>> newer linker.
>
> The new compiler still needs to be able to produce code that deploys back to 10.5. The newer linker will synthesize the stubs. I think you are right that the code will still run. But it would be nice to be able to verify it.

Just a nit, 10.5 is darwin9, which is not modified by this patch at
all. Currently we only produce stubs for darwin8 and older (OS X
10.4).

Cheers,
Rafael