[llvm] r186197 - Change llvm-ar to use lib/Object.

[Rafael Espíndola]

> This is awesome. =D

Thanks.

> Any chance you have performance numbers for binutils 'ar', old llvm-ar, and
> lib/Object llvm-ar? I'd like to make sure we can use this new fancy 'ar'
> tool without any issues even in non-LTO cases.

So far llvm-ar doesn't know how to create a symbol table (that is
fairly high up on the TODO list), so the only benchmark possible is
creating an archive without it, which is not that interesting. In any
case, I timed recreating a debug version of libclangSema.a in a tmpfs:

* gnu ar: 0m0.176s
* new llvm-ar:  0m0.137s
* old llvm-ar: 0m0.156s

I do expect the difference to go up when we add symbol table creation,
specially when IL files are involved.

Cheers,
Rafael