LLD is not available with `download-ci-llvm`

[Aaron1011]

When download-ci-llvm=true is set, lld is not available in build/x86_64-unknown-linux-gnu/ci-llvm/bin. This makes it more difficult to use a stage1 compiler to cross-compile to platforms that use LLD by default (like wasm32-unknonwn-unknown), as the linker needs to be manually overridden in a .cargo/config file.

If we have the CI budget available, it would be useful to build LLD along with LLVM, and make it available in the archive downloaded by x.py.

[Mark-Simulacrum]

We just need to adjust the component creation to include LLD -- at least on x86_64-unknown-linux-gnu it's already built.