[lld] r249752 - Revert: r249728 - Roll back r249726 and r249723 because they broke buildbots.

[Rafael Espíndola via llvm-commits]

> Right. There are two issues here:
>
>  1. Can we always used a fixed VAStart address?
>
>  2. Should it be a target property?
>
> The answer, at least in the long run, is certainly no. There are plenty of applications that run under embedded (or other light-weight) kernels that need the ability to specify a starting virtual address in order to function correctly (or, at least, to not waste huge amounts of memory).

Completely agree. At some point we will need to support setting it in
linker scripts and options like -Ttext.

> However, regarding (2), this seems much less clear. It might be more natural for this to be a property of the target operating system more than the target, for example. But, in any case, lacking specific documentation and/or understanding on how to choose the values, I'll revert this.

Exactly. I also expect that at some point some customization will be
needed here. So far we haven't hit that yet, so it is hard to know
exactly what customization and until we do we should keep the code
simple.

Thanks,
Rafael