[patch] Drop support for creating $subs

[Rafael Espíndola via llvm-commits]

>> +Nick, so he can correct me if I get this horribly wrong or something. ;)
>>
>> Policy-wise, this seems fine to me.
>>
>> We’re not actively testing against the 10.4 linker or anything like that. We, generally speaking, care about the latest tools being able to produce executables (including dylibs and bundles) that can run on older systems. Mixing and matching tools from different releases isn’t a typical scenario. The introduction of new load commands is a good example of that.
>
>
> So Nick, is Grosboch's analysis correct?

Post WWDC ping.

Cheers,
Rafael