Example clang/rust/go toolchain

[adam-singer]

Description

Creating an experimental toolchain that contains clang/rust/go.

Fixes https://github.com/TraceMachina/nativelink/issues/1201

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

nix build .#nativelink-worker-buck2-toolchain.copyToDockerDaemon
docker run -it <hash> /bin/sh
sh-5.2$ clang --version
clang version 17.0.6
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /nix/store/c0za00cgiclxd41cz72qlxvw845hgp4f-clang-17.0.6/bin
sh-5.2$ rustc --version
rustc 1.79.0-nightly (aed2187d5 2024-04-27)
sh-5.2$ go version
go version go1.22.5 linux/amd64

Checklist

• [ ] Updated documentation if needed
• [ ] Tests added/amended
• [ ] bazel test //... passes locally
• [ ] PR is contained in a single commit, using git amend see some docs

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This change is