[llvm] r216905 - Replace -use-init-array with -use-ctors.

[Rafael Espíndola]

>> Clang is not affected by this. It has its own fancier logic.
>
> IMO the default is wrong. The list of systems that allow .init_array at least
> for ELF is quite small. IIRC Linux, DragonFly and AArch64 in general.

On the llvm using .init_array seems more convenient

* It is what newer systems are normally using.
* Most developers are on systems with .init_array.

Case in point, I implemented this after being surprised to see a
.ctors on pr20793.

Another option would be to compute the default based on the triple and
share the logic with clang, but I am not sure where to put it.

Cheers,
Rafael