[lld] [lld][MachO]Multi-threaded i/o. Twice as fast linking a large project. (PR #147134)

[Daniel Rodríguez Troitiño via llvm-commits]

https://github.com/drodriguez commented:

@ellishg 
> By the way, I found TaskQueue in Support/ which seems to do what we want. Could we use that?
https://github.com/microsoft/llvm/blob/f270d88e8d2c496285111e9a600513d460df4633/include/llvm/Support/TaskQueue.h#L32-L35

That seems from a fork of LLVM. I couldn't find a good parallel queue abstraction already in LLVM. `Parallel.h` is the closest, with some other bits in `Threading.h` and `ThreadPool.h` which might be helpful.

https://github.com/llvm/llvm-project/pull/147134