Only copy LLVM into rust-dev with internal LLVM

[Mark-Simulacrum]

This avoids needing to figure out where to locate each of the components with an
external LLVM. This component isn't manifested for rustup consumption and
generally shouldn't matter for anyone except Rust's CI, so it is fine for it to not be
complete elsewhere.

Fixes #76572.

r? @alexcrichton

[semarie]

does it make sens to even build it for external llvm ? the tarball will be almost empty. But maybe it will be extended later ?

LlvmTools uses the following:

        /* run only if llvm-config isn't used */
        if let Some(config) = builder.config.target_config.get(&target) {
            if let Some(ref _s) = config.llvm_config {
                builder.info(&format!("Skipping LlvmTools ({}): external LLVM", target));
                return None;
            }
        }

[Mark-Simulacrum]

Yeah, I am thinking that we'll expand it eventually but for now I think it does indeed make sense to just skip it entirely.

[alexcrichton]

Hm I don't think I've kept up enough with this over the past, I'm not sure what RustDev is :(. Can you provide a small description of what it's used for?

[Mark-Simulacrum]

It's the component intended for aiding rustc development, specifically providing pre-compiled LLVMs to developers (along with llvm-config and header files, basically enough for librustc_llvm to compile and link to this LLVM). It was just added a few days ago in #76332

[alexcrichton]

@bors: r+

Ok cool, makes sense to me!

[bors]

📌 Commit 4f2d941 has been approved by alexcrichton

[bors]

⌛ Testing commit 4f2d941 with merge d778203...

[bors]

☀️ Test successful - checks-actions, checks-azure
Approved by: alexcrichton
Pushing d778203 to master...