[lld] [lld] enable installing lld headers as part of distribution (PR #127123)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> > LLVM_DISTRIBUTION_COMPONENTS=clang;clang-headers;lld installs clang headers. This PR makes lld-headers installs lld headers.
> 
> Sorry I don't understand `This PR makes lld-headers installs lld headers.`.
> 
> Do you mean that `LLVM_DISTRIBUTION_COMPONENTS=clang;clang-headers;lld` **shouldn't** install `lld-headers`?

Right. lld headers should only be installed when `lld-headers` is present.

> That's fine I can fix that (I'm just trying to understand what exactly the change requested is).



https://github.com/llvm/llvm-project/pull/127123